M10 ITB´s

[Andy335Touring]

jap spaers not includet

Please mind that I'm not english. Can you explain what is "jap spaers"?
Jan

erm i'm not sure if this blokes first language(sp?) is English as his posts don't make much sense ?

[Yaninnya]

erm i'm not sure if this blokes first language(sp?) is English as his posts don't make much sense ?

Yes, I allready noticed that his posts are, erm, a little bit different. But the way how he is writing looks like he is English.
Jan

[Gunni]

Again,

you don´t need ITB´s to get straight runners for pulse effects.

Of course the same does for FI engines, only the pressure in front of the throttle bodie/s is so much greater, that the time of rebalancing the air pressure for air flow is so much shorter.

The most obvious + of ITB´s in a FI engine is to diminish turbo lag, as it´s obviously the air in the turbo manifold that pushes on the blades of the turbine, the sooner you get more air their the sooner you get boost, and we already know that the ITB´s are quicker then a regular single throttle plate.

[Yaninnya]

Again,
you don´t need ITB´s to get straight runners for pulse effects.

You wrote it in your previous post. So I ask you again: explain how? Because it is just imposible (exept real huge plenam which just is too big for most cars)

Of course the same does for FI engines, only the pressure in front of the throttle bodie/s is so much greater, that the time of rebalancing the air pressure for air flow is so much shorter.

Mate, do you know what you are talking about? I just ask you: tell me what pressure can you get from pressure pulses? And please anwer me on that question just strait without any "maybe" or "it depends". O.K.?

The most obvious + of ITB´s in a FI engine is to diminish turbo lag, as it´s obviously the air in the turbo manifold that pushes on the blades of the turbine, the sooner you get more air their the sooner you get boost,

Did you read my previous post? It looks like not. I will ask you again what amount of air is using the engine each second with 0.7 bar boost at 4000 rpm? And then compare the result with your theory.

and we already know that the ITB´s are quicker then a regular single throttle plate.

No, I don't. That's tipical demagoguery. Not in technical. Facts please.
A little bit less friendly Jan

[Turbo-Brown]

After that this vave is pushing the mixture to this cylinder. And because the vave is moving with qute high speed (sonic) the inlet pipes needs to be very short so it is imposible to use single throttle.Thats the very short and extremally basic theory why in na engines ITB are working.
Now tell me how it can work in inlet with compressor wheel? You have the pressure (or lack of) in the whole inlet behind turbo. No pulses at all.
Can you explain me this?

Hmmm, the length of the inlet runner and whether or not you have ITBs are entirely independent, and the effects of pulse tuning are largely the same regardless of whether you have a plenum style intake with a single throttle or ITBs. I'm sure you know you can tune for pretty much any reflected pulse too (albeit weaker pulses) so as to spread your power around a bit more, rather than just going all out to get the 1st reflected with short runners over a very narrow and very high crank speed range.

I'm not sure how adding a compressor wheel into the intake system would eliminate any pulsing in the intake system either. Sure it poses a tiny restriction to flow, but the pulsing of the air in the inlet will always be there.

This is a discussion, as I would have with some of my friends, where our opinions differ, I wouldn't fall out with a friend over a difference of opinion so lets all be calm and smiley when we're putting our points across

[Gunni]

Here is a tought,,,,,,,,,,,
if you monitor the PWM on a electronic boost contoller you could see if at one point the wastegate would
waste more to maintain same boost, that would indicate that pressure pulses where raising the boost.

Obviosuly only measurable at the valves tough and not in the intake.

[Gunni]

Again,
you don´t need ITB´s to get straight runners for pulse effects.

You wrote it in your previous post. So I ask you again: explain how? Because it is just imposible (exept real huge plenam which just is too big for most cars)

Of course the same does for FI engines, only the pressure in front of the throttle bodie/s is so much greater, that the time of rebalancing the air pressure for air flow is so much shorter.

Mate, do you know what you are talking about? I just ask you: tell me what pressure can you get from pressure pulses? And please anwer me on that question just strait without any "maybe" or "it depends". O.K.?

The most obvious + of ITB´s in a FI engine is to diminish turbo lag, as it´s obviously the air in the turbo manifold that pushes on the blades of the turbine, the sooner you get more air their the sooner you get boost,

Did you read my previous post? It looks like not. I will ask you again what amount of air is using the engine each second with 0.7 bar boost at 4000 rpm? And then compare the result with your theory.

and we already know that the ITB´s are quicker then a regular single throttle plate.

No, I don't. That's tipical demagoguery. Not in technical. Facts please.
A little bit less friendly Jan

#1, check out some swedish turbo monsters,
they are ,, running runners, and single throttle body setups, and big plenums,

#2, check the post I just made, that is the only way to monitor any pulses at all,

#3, That is a arbitary question, you can´t tell me how much airflow is at 0.7bar boost at 4000rpm, as you are forgetting two things,
VE and engine size.

#4, Again datalogging air pressure at the valves and TPS position will reveal the time diffrence it takes for a single throttle to raise air pressure vs. ITB´s,

I don´t need to put up any calculations because simple theory explains the situation..

Can you explain the why and why not in theory?

[oakey]

a VERY interesting read all this!

[Gunni]

I love these discussions.
opens peoples eyes.

[Turbo-Brown]

I love things like this, as long as no body's sitting at home getting mad about other people not agreeing with them.

Sounds like Gunni and I are both thinking along the same lines here.

[Gunni]

great minds think alike is what you meant? ;)

[Yaninnya]

I love things like this, as long as no body's sitting at home getting mad about other people not agreeing with them.

I'm not going mad at all! I'm only trying to show that a lot of "gospel" in engine modifications are, let's say, wrong. I was trying to help, I explained why it will not work. I didn't hear any real arguments against my point of view.
My intention is to help and save loads of money to less experience forum members. Nothing else. If someone wants to built the engine with fi and itb - it's his decision, but please do not try to explain that decision with technical reasons.
People are copying some specifications (solutions? I can't find the correct word) without any critics. I have too much my own expieriences to belive that anything new what I see is good. Sorry, but as far as anyone will explain me how it can improove good standard setup, I will be saying: no, it will not give you anything.
I only affraid that this time my english is not easy to understand. Sorry.
Not mad Jan

[Turbo-Brown]

OK, getting away from both our experiences and opinions on the subject: Why is it that there have been quite a few engines designed and built over the years, for both road and race, which have had turbochargers AND ITBs?

There are the examples I gave over the page with Nissan, Peugeot in the T16, Bugatti with the EB110 and various others including Porsche TAG back in the 80's when they supplied McLaren with a twin turbo V6 featuring ITBs.

Various Indy-cars also have had turbos and ITBs.

If there was no merrit to the idea, why would this kind of thing have been used on F1 engines of all things?!

I think the language barrier has perhaps played a part (and your English is very good by the way and my explanations of my points have been less than perfect!) but I've not seen a good explanation of why you think the idea doesn't work

[e30world]

bmw engine only

[Turbo-Brown]

bmw engine only

You've lost me dude

[Yaninnya]

OK, getting away from both our experiences and opinions on the subject: Why is it that there have been quite a few engines designed and built over the years, for both road and race, which have had turbochargers AND ITBs?

Mostly regulations. In Indy was restriction of maximum boost pressure.

There are the examples I gave over the page with Nissan, Peugeot in the T16, Bugatti with the EB110 and various others including Porsche TAG back in the 80's when they supplied McLaren with a twin turbo V6 featuring ITBs. Various Indy-cars also have had turbos and ITBs. If there was no merrit to the idea, why would this kind of thing have been used on F1 engines of all things?!

Yes but from other side why even F1 engines where with two (one per each cylinder row) TB? Remember, that in the past a lot simple solutions where uknown. In group B cars with huge and heavy internals turbos the lag was huge (thats why Delta S4 was with mechanical Roots compresor and turbo). Now with simple and cheap ALS you can have no lag at all (as I written before, I was driving feew cars with ALS, one was even fast road!, and it is my own experience). Of course the live of turbo is very short but the effect is just unbeliveable. Also remember that F1 engines has over 1200 bhp from only 1.5 liter capacity (thats official, rumours where that on the end of turbo era in F1 it was around 1500 bhp on race and over 1800 bhp on trainings). It is from 800 bhp/l to 1200 bhp/l! How many cars on our forum have over 200 bhp/l? You know what I mean? These engines where running on boost up to 4.5 bar. So imagine what amount of air (and fuel) they where using.

I think the language barrier has perhaps played a part (and your English is very good by the way and my explanations of my points have been less than perfect!) but I've not seen a good explanation of why you think the idea doesn't work

Firs of all the old rule KISS (keep it simple, stupid): if I don't need something, I'm not using it. If something is working absolutely perfect do not modify it. One of main rules of the best engines is simplicity. Look at YB Cossie engine: super simple and near idiotproof.
Next thing: do not belive what you are reading in magazines and what people are saying about their engines. From my observation, around 60% is pure bullshit (specially the max power, torque, acceleration and max speed). The best example is american twin turbo M5 E60 with turbos under... rear bumper. The bloke was saying that there is no lag (with over 12 meters of inlet system and around 5 meters from exhaust ports to turbo) and max speed is well over 240 mph. Dreamer... Or compare the articles about Ant car. Interesting?
About better response with ITB in fi BMW engines (i.e. Toby Unna car): you must remeber that near all (or even all I think) single TB inlet manifolds where designed for na. They are hopeless for fi use! First make proper manifold for fi and than compare it with ITB. You will be suprised.
I just touched the whole problem. I think that even the whole night (with some beer ) will be too short for the discussion about na and fi intakes (and exhausts because they can't exist separately), differences between them, why something is working in na and not in fi and inversely. And to be onest we shoud also touch ports, cams, CR, maping and feew other. The whole problem is so complicated that quite often when you are changing one part you need to change feew others.
I'm 37, from over 18 years I'm building the engines and still I can't say that I'm engine specialist. I'm just a little bit smarter than the others.
I know that there a lot of mindshorts(is it english?) in my post but it is just imposible to explain everything in one post. But I always ready to help or advice. That's for sure.
Jan

[Scrotty]

bmw engine only

what IS this bloke on....?

[Scrotty]

you must remeber that near all (or even all I think) single TB inlet manifolds where designed for na

good point there, i remember a sweedish guy that built a 600bhp calibra , using the C20LET, and he literaly made his own inlet manifold with tapered plenum...just some sheet steel+lots of welds...done a treat
but i wouldnt say its always the best solution, the japs design the most reliable engines in the world, and the GTR32 was one of the best cars from rice land....its twin turbo, has been tuned well over 1000bhp on the road and has ITB's...for that reason and that reason alone i will believe ITB's are benifitail to forced induction engines...

back to your KISS rule jan, the r32 was also one of THE most complicated setups, the electronic 4wd and all that jap crap, it was all needed, and all worked (well its jap) so the car (with other factors of course) was a success. i think its simple...theres more than one answer here....but the answer that is important is not which setup will result in the most power over the rev range, but which is actaly worth implimenting...soo your going to covert a M10 to f.i.....and the standard intake dosnt flow well enough/pluse blah blah/whatever reason, its crap......WHAT DO YOU DO? make a one off manifold with plenum and single tb, or just buy a pressure rated ITB setup and manifold, then get mapping?

jan, mr brown etc know far more than i....but what if maybe his single tb idea has truth to it? once apon a time we thought the world was flat ffs

anyways you lot carry on, while us lot read and learn, from 2 different sides its the best way to learn shizz like this.i wonder what random crap e30world will say next

[Turbo-Brown]

I still haven't grasped Jan's arguement for why ITBs wouldn't work on an FI engine. I don't understand why he's stated that pulse tuning won't work with FI at all.

Jan, can you explain again for me in a kind of A-B-C- fashion why you believe you can't use pulse tuning in FI?

[Gunni]

Also don´t forget throttle response wich IS the reason for ITB´s,
nobody would design a multhi throttle intake if there was no merit

itb´s are NOT specifically used for pulse tuning, as even the M20 manifolds show obvious diffrences in runner size and lenght to use pulse tuning, same goes for obvious diffrences in M42 and M44 intake systems,

in a street car I would not use a ITB setup unless the engine already had it, but in a race car where throttle response is absolutly needed I would , and they do...

[Yaninnya]

I still haven't grasped Jan's arguement for why ITBs wouldn't work on an FI engine.

Hold on, I didn't say that:

There is no any technical reasons for fiting throttle bodies on turbo engine.

Which means that the engine will be runing fine only you will not have any gains. I think you will agree with me that it is big difference.

I don't understand why he's stated that pulse tuning won't work with FI at all.
Jan, can you explain again for me in a kind of A-B-C- fashion why you believe you can't use pulse tuning in FI?

I'll try:
How it is in na engine I explained in one of my previous post so that some base to futher explains.
First of all in practise it is near imposible to fabricate the inlet manifold with equal lenght pipes to each cylinder. I hope that you will agree with me (I saw somwhere in one of BMW magazine your car, so I know that you have good practise). Second, let assume that we have that manifold, and it is pulsating perfect. But on the way to the begining of the whole inlet system is... ic. Try to imagine what happening when the wave is reching ic. Do you know that air and water waves are in practise the same? Quite often the water was using for aerodynamics resarch. So the ic is like big breakwater (the compressor wheel is exactly the same). Of course you can still design the manifold with standing wave, but it is not related to pulses.
I'm not heapy with this explain, so if something is not clear, please ask.

Also don´t forget throttle response wich IS the reason for ITB´s,

You are like broken record. I explain before that it is not truth.

nobody would design a multhi throttle intake if there was no merit

On what world you are living, mate?!

itb´s are NOT specifically used for pulse tuning

Oh, yeah? But you still don't want to tell me how you are going to design the manifold with single tb and ca. 300 mm lenght.

as even the M20 manifolds show obvious diffrences in runner size and lenght to use pulse tuning, same goes for obvious diffrences in M42 and M44 intake systems,

Are you trying to say that i.e. M20 somebody was designed with dynamic induction in mind?
Jan

[Yaninnya]

the r32 was also one of THE most complicated setups, the electronic 4wd and all that jap crap, it was all needed, and all worked (well its jap) so the car (with other factors of course) was a success.

And on race track was slower than super simple Cossie RS 500 (Australia, Bathurst).
Jan

[Gunni]

Here , one throttle body, individual runners used.

If you examine the 3 most popular M20 intake manifolds,
325i, ETA and 323i, they are all diffrent in all aspects.
Runner lenght, the runner size and chamber size,
going even further to throttle body size,
And you think that there is another reason for the diffrence then pulse tuning??

2 questions,
Only ITB´s are used in pulse tuning and not regular intake manifolds?
Where have you shown me that ITB´s are not used for throttle response only?

And don´t give me any runnarounds like the fact I´m a broken record .

What I´m sure your not getting is the results of pulse tuning can not be measured by a MAP sensor in the intake manifold, the manifold pressure needs to be measured real close to the intake valve and compared to the manifold pressure, I´m 100% sure that you do get a measurable diffrence, showing up as more air pressure closer to the valve at the rpm point where the pulses are working ..

[Turbo-Brown]

I have empirical data to suggest that even under boost, you get pulsing in the inlet runners.

This has been observed on myown setup where the pressure signals for the MAP sensor and gauge are taken from within 30mm of the cylinder head.

Second, let assume that we have that manifold, and it is pulsating perfect. But on the way to the begining of the whole inlet system is... ic. Try to imagine what happening when the wave is reching ic. Do you know that air and water waves are in practise the same? Quite often the water was using for aerodynamics resarch. So the ic is like big breakwater (the compressor wheel is exactly the same).

That sounds to me like you stating that if there aren't pulses at one point in the system, there can't be pulses at any other, i.e. the inlet runners? Surely an air filter would act to damp out pulses in an NA system too?

I wouldn't necessarily agree that it's difficult to get the inlet runners equal. I managed it on mine easily enough. No doubt there are lots of applications where it is trickier though.

[Yaninnya]

Sorry for delay, I was extremally bussy last feew days.

I have empirical data to suggest that even under boost, you get pulsing in the inlet runners.
This has been observed on myown setup where the pressure signals for the MAP sensor and gauge are taken from within 30mm of the cylinder head.

I read again our posts and I found that I didn't wrote enough clear how the waves pulses working. The most important is that the vaccum wave needs to reach open space to change to pressure wave. So when vaves are hiting the compressor wheel in fi engine they are reflecting(changing direction? - I can't find the perfect word) but still as pressure wave - not vaccum. Thats the reason why you messured the pulsing.

Second, let assume that we have that manifold, and it is pulsating perfect. But on the way to the begining of the whole inlet system is... ic. Try to imagine what happening when the wave is reching ic. Do you know that air and water waves are in practise the same? Quite often the water was using for aerodynamics resarch. So the ic is like big breakwater (the compressor wheel is exactly the same).

That sounds to me like you stating that if there aren't pulses at one point in the system, there can't be pulses at any other, i.e. the inlet runners?

To get the change of wave (pressure to vaccum) it needs to "hit" open space, even large plenam is not enough to do this.

Surely an air filter would act to damp out pulses in an NA system too?

No, the air is passing throu air filter and can't pass the ic or compressor wheel propeler walls. That is quite different, isin't it?

I wouldn't necessarily agree that it's difficult to get the inlet runners equal. I managed it on mine easily enough. No doubt there are lots of applications where it is trickier though.

I saw your car in last PPC magazine and I can't agree with you that inlets in your engine are equal. Compare the lengh of inlet for 1 cylinder and others. There diference around 300 - 350 mm between 1 and 6. You can't count only the distance between valve seat and plenham. Your plenham is far too small to work as open space.
BTW: Absolutely no offence but why you have such a mess under the bonnet? I know what a huge job is done there but with everything fited properly it is far easyer to work on it during any underbonnet job.

Here , one throttle body, individual runners used.

You really don't know what equal lenght intakes means, because on this S38 the intake lengh of sixth cylinder is longer ca. 500 mm than on first one. If you think that you can count only short part from plenham (Is it correct word?) to cylinder head (or more percisly to valve seat) than you are complitely wrong. You need really, really big volume to fool the wave and to change it direction.

If you examine the 3 most popular M20 intake manifolds,
325i, ETA and 323i, they are all diffrent in all aspects.
Runner lenght, the runner size and chamber size,
going even further to throttle body size,
And you think that there is another reason for the diffrence then pulse tuning??

Of course! Did you heard about inlet volume and how it changing the engine flexibility? I'm thinking and can't remember any standard engine in which dynamic induction was used.

Only ITB´s are used in pulse tuning and not regular intake manifolds?
Where have you shown me that ITB´s are not used for throttle response only?

Please, there are a lot of books about inlet systems in engines (na and fi). My english is not enough good to explain this and also it is just impossible to squeeze the whole theory on the forum. I was trying to explain as simple and short as I can.

And don´t give me any runnarounds like the fact I´m a broken record .

Why? You are repeating something what you are heard from someone without understanding it. When I'm trying to show you that that theory is based on wrong base you don't want to analyze it. You written that it is not so strait. Just try and you will be very suprised.
A little tired but friendly as ussual
Jan

[Turbo-Brown]

Ah ha!

I think I'm starting to understand the points we disagree on

It sounds to me (correct me if I'm wrong) like you're saying that each individual wave must travel the entire length of the inlet system before it can be reflected back and do any good in the engine.

If I do understand what you're saying, that's not right. Any wave, water or otherwise will initiate another wave of smaller amplitude given an abrupt enough section change such as an inlet trumpet. That weaker wave will travel off through the plenum and get to the filter, IC, compressor or whatever, changing sign and rattling around off anything in it's way. However, there will still be a reflected pulse in the trumpet and that's all an NA engine can use. In the same way, a FI engine can make use of the same reflected pulse.

The weaker resultant wave can also be used if the wall of the plenum is close enough to the trumpet (and I suspect this is the case with the S38 which has a very close wall) where the first pulse initiates the weaker second pulse upon arrival at the trumpet mouth and is reflected back, and the weaker pulse bounces off the wall of the plenum so that it can be added to the first pulse.....over a very narrow engine speed range.

Now is it me, or have we wandered completely off the topic of ITBs on FI engines, and become solely obsessed with whether or not you can use pulse tuning on an FI engine?

No offence taken! I apologise to everyone for the mess in my engine bay. It's mainly caused by the HT leads which are far too long and are wrapped around everything to stop them flapping about. Should probably shorten them a bit, but I'm too busy making things for people!

[Yaninnya]

Ah ha!
I think I'm starting to understand the points we disagree on

I told you! I'm working in TVR service here and even that I don't have problems with "normal" english near at all when the more technical problem is becoming it is not so simple to explain my boss. Sometimes the best way is to show what I mean.

It sounds to me (correct me if I'm wrong) like you're saying that each individual wave must travel the entire length of the inlet system before it can be reflected back and do any good in the engine.

Not exactly. It needs to if you want it to change in to pressure wave. Otherwise it still be the vaccum. You can use it (when it will reflect from closed inlet valve just before its opening it will helps - I hope you understand what I mean). More or less to get 100% from wave pulses it needs to reach the atmosfere (open space).
Of course it is so simple in theory and practice is different story. Sometimes in practise you need complitely different lenghts (like na M10 on ITB! Extremally long inlet pipes - around 550 mm are working the best - and nobody knows why) or in Ford YB engine the exhaust shoud have around 2000 mm from turbo flange to exit (why?!) or just pulses are not working near at all. I was going mad with Fiat Fire rally engine with dual TB where pulses where "mixing" and I didn't found the configuration which was sensible better then anything else when other very similar engine was beautyfull pulsing with just small plenham over inlet cones.

That weaker wave will travel off through the plenum and get to the filter, IC, compressor or whatever, changing sign and rattling around off anything in it's way.

That's the point where we have different opinions. My practise shows that you need really huge difference in crosssection (or better in capacity of part of inlet system) to change sign. The theory is not so sure too (I was reading a lot about it years ago and some of authors are saying that it is working as I described and some of them that it needs just more than 2/3 crosssection - if I remember now correctly - I wasn't building a na engine with r&d work for over three years).

The weaker resultant wave can also be used if the wall of the plenum is close enough to the trumpet (and I suspect this is the case with the S38 which has a very close wall) where the first pulse initiates the weaker second pulse upon arrival at the trumpet mouth and is reflected back, and the weaker pulse bounces off the wall of the plenum so that it can be added to the first pulse.....over a very narrow engine speed range.

I wasn't measuring this in S38 but BMW likes to design the engines in 100% (specially S engines) so most probablly yes. My point is that in fi engine it is just so tiny, tiny gain when you compare it with loses because of inlet shape that it is not worth.

Now is it me, or have we wandered completely off the topic of ITBs on FI engines, and become solely obsessed with whether or not you can use pulse tuning on an FI engine?

No offence taken! I apologise to everyone for the mess in my engine bay. It's mainly caused by the HT leads which are far too long and are wrapped around everything to stop them flapping about. Should probably shorten them a bit, but I'm too busy making things for people!

As I told you: I know what massive work is there just after first look. And I'm very impressive because all forums are full of people which are saying "what a crap! you done this and that wrong!" but they cant do anything by themselfs and you are one of not so many persons which is not only talking. I just like to finish the engine that people will be saying "is it factory option?". And I know wery well how it is with your own car and time.
BTW: At what revs you can feel increase of torque with you setup (the boost pressure is rising)? What are the specs of turbos (A/R, wheels trims)?
Jan

[Turbo-Brown]

Crikey, missed this!

Now how is it we all forgot to talk about air velocity in the runners and how you can potentially get away with longer runners on a turbocharged engine to augment low end torque whilst not sacrificing too much top end power as the pressure difference across the runners makes up the deficit.

Not strictly related to the application of ITBs to FI, but think the subject has changed to runner lengths now.

Will have to dig out the turbo specs (although I don't know what trims they are unfortunately)

Here's the power plot though with boost at the bottom:

[Gunni]

Thats a funny dyno chart.
Doesn´t the HP ever peak on your setup?

[Turbo-Brown]

Nope, it even starts to climb again just before the injectors ran out of go

Free breathing it seems, is not without it's merrits.

Have a look at Blingsta's plot (think he's got one kicking about with 7psi) and the difference in peak power and it's delivery.

[Gunni]

Wich would that be?
You have more torque everywhere in the chart then a stock B25 has at peak torque!

can´t see anything wrong there

[Yaninnya]

Will have to dig out the turbo specs (although I don't know what trims they are unfortunately)

They are T2 or T25 (I hope that I remember corectly and they are not GT series...)? Do you remember from what car are they coming from?

Here's the power plot though with boost at the bottom:

Very smooth (did Dave Walker mapped it?), I'm impresed! It's looks like you can increase the boost pressure a lot (or fit a compressor housings with a smaller A/R, than the increase of pressure will be at lower revs). So it looks like on the road you fill the kick at around 2700 rpm? What CR is in your engine and what specs cam?
Jan

[stonesie]

I think this comes close to what Yaninnya means by equal length inlet runners (on a mazda 323's 1.5 engine)



Very interesting read this

[Turbo-Brown]

Wowzers, that's one complex casting!

Jan, the turbos came from a Skyline so I think they're a funny spec of T25 with tiny little hot sides.

I could perhaps have taken another 3psi if the injectors were larger, but they ended up going to 97% duty as it was.

The engine's a standard early spec M20B25 with a 9.7:1 compression ratio and standard cam.

Anyway, all this lot's moving on as I'm working on a twin sequential setup now in the hope of getting boost from idle to the red line

[stonesie]

Its an ebay pic but my bosses wife used to have 1 of those mazdas with that engine and that inlet is equal length pipes welded to the smallest plennum i have ever seen on a car then bolted to the single throttle body, constructed more like a 4-1 exhaust manifold i thought.

For a 1.5 car of its size it went well



To go back to the comparisons between single throttle body and ITB's.... on a few cars (ford KA 1.3 is a prime example) if you open the throttle quickly there is a hiss noticeably before the engine reacts, i assume this is the air pressure equalising in the manifold compared to in the uncontrolled portion of the inlet system (ambiant atmospheric pressure or near-as-makes-no-differance)

As i figure it, simplisticly as it may be, on a ITB set-up the controlled portion is much smaller so it takes much less time for the pressures to equalise giving the better throttle responce i have no doubt that a delay still exists but it will be much smaller and probably not noticeable