New Manifold makes +18 BHP on stock 325i with dyno

[chip-3door]

decking the head/block quickly ruins the cam timing. The belt will not line up on the cam gear at TDC. This isn't the place to look for compression.

Either way there is very little to be gained % wise by bumping up compression. In fact the only thing you stand to gain for sure is a detonation problem.

Thats just a nonsense, you will improve the squish band if you run the pistons just out the top of the deck.

And cam timing isnt effected in the slightest as you just alter the vernier a degree or two to compensate (not like any muppet is going to try and build a decent power engine and not fit a vernier obviously!)

[Jordan]

Decking the head and block looking for compression is just halfass in my opinion. Fitting custom pistons is proper.

What would I know though, I only have $1k USD worth of custom 10.2:1 JE pistons with stupid small quench clearances in my 2.8l

[chip-3door]

For a measly 20% increase on standrad, i dont believe that you need to go down the route of custom pistons.

Not saying they dont work, because they do, ive used them in many engines ive built myself, but its not the only way to raise CR

Building a big budget 2.8 is a different kettle of fish to building a low budget moderately powered 2.5

People were specifically asking for the more economical ways of doing things, so i was giving those options.

Try and open your eyes beyond just your own engine spec to other possibilities!

Did you build your own engine, cause it looks great in the pics on the link in your sig

[Jordan]

Yes, I do all my own work. I have high resolution (7.2MP) copies of all images on my CarDomain site.

Decking the block and head to raise compression.. it does work, but again.. its just not the right way to do it. Decking the head just a little (to factory min thickness) is fine. But decking the block is a no no in my opinion. Even if you use a offset dowel pin to replace the one on the camgear and give it back its proper timing... things still aren't right.

Stock compression is 8.8:1 on a m20b25. Increase this to 10:1 and you will observe a 4 or 5 percent increase in horsepower. Further increasing the compression to 11:1 might only provide a 2 or 2.5 percent increase over that.

Compression alone doesn't really make power, certainly not enough to deal with the headaches that come with it! M20's do not respond well to compression. They have no knock sensors, and high enough octane fuel simply is not available.

The combustion chamber design isn't favorable for increased compression either. There was a reason BMW kicked the m20's out of the factory with 8.8:1. I've heard numerous bone stock good running m20b25's running on 87octane on a hot day pinging under load! This is exactly what I am talking about.

When I built my 2.8L (10.2:1) I had the stock chip. It pinged like crazy at all throttle positions. This was with 92 octane fuel. Only after I did the MAF conversion and installed/tuned my UNICHIP engine management was I able to retard the timing, and give the motor proper A/F ratios to curb the pinging.

I've since built a completely new 885 head from scratching, porting it out to the max and reshaping and polishing the chambers to be as compression friendly as possible

I'm looking forward to my next day long dyno tuning session in 2 weeks to retune the engine and pull every last ounce of detonation free power out of it.

[M5pilot]

I'd have to agree that Custom pistons is the way forward to achieving big power on an m20.

However, sticking to the topic - M20 2.5 with 200 BHP or near enough which has almost stock driveability and much better top end power is what we are aiming for and hopefully this manifold should make life a bit easier to achieve that goal.

[MONSPORT42]

As far as i'm aware Unichips are only used for MAF conversions because Motronic can't read the signals and vice versa

[chip-3door]

Yes, I do all my own work. I have high resolution (7.2MP) copies of all images on my CarDomain site.

Decking the block and head to raise compression.. it does work, but again.. its just not the right way to do it. Decking the head just a little (to factory min thickness) is fine. But decking the block is a no no in my opinion. Even if you use a offset dowel pin to replace the one on the camgear and give it back its proper timing... things still aren't right.

Stock compression is 8.8:1 on a m20b25. Increase this to 10:1 and you will observe a 4 or 5 percent increase in horsepower. Further increasing the compression to 11:1 might only provide a 2 or 2.5 percent increase over that.

Compression alone doesn't really make power, certainly not enough to deal with the headaches that come with it! M20's do not respond well to compression. They have no knock sensors, and high enough octane fuel simply is not available.

The combustion chamber design isn't favorable for increased compression either. There was a reason BMW kicked the m20's out of the factory with 8.8:1. I've heard numerous bone stock good running m20b25's running on 87octane on a hot day pinging under load! This is exactly what I am talking about.

When I built my 2.8L (10.2:1) I had the stock chip. It pinged like crazy at all throttle positions. This was with 92 octane fuel. Only after I did the MAF conversion and installed/tuned my UNICHIP engine management was I able to retard the timing, and give the motor proper A/F ratios to curb the pinging.

I've since built a completely new 885 head from scratching, porting it out to the max and reshaping and polishing the chambers to be as compression friendly as possible

I'm looking forward to my next day long dyno tuning session in 2 weeks to retune the engine and pull every last ounce of detonation free power out of it.

Decking the block is a no-no for what reason?

As for the M20 not liking compression, thats all down to cam choice and head mods, same with any engine, go for a lairy cam that shifts the power up the range and you need more CR to get the most from it.

I agree on the fuel though, modern stuff is crap!

Bring back 100 octane leaded i say!

[Dan318-is]

interesting thread

just replying so i can get notifications as this is a useful source of knowledge for someone profoundly stupid like me

[chip-3door]

Argos, unichips arent as bad as you make out, its possible to get good results from them, but yes fundamentally it is just a nasty bodge, especially as any change in timing results in a shift in the position within the induction stroke timebase at which the injector fires, far from ideal!

A series are indeed litter, 3 bearings on the crank instead of 5 and 5 ports on the head instead of 8, my point was if i (and you by the sounds of it) can get that sort of bhp per litre from old tat like that it should be easy from a M20, which although not great by modern standards is still well ahead of the old A series.

Your a bit wide of the mark on the torque comments, geared correctly its BHP not torque thats the king for acceleration, as torque @ wheels is what counts and thats a product of gearing and bhp, not of flywheel torque.

[M5pilot]

Just a reply to a few comments Argos makes:

Adams car makes 204 bhp not because its fitted with a unichip but because of something else (which we dont really know). Why is it that many other cars with Unichips which are 2.7's make well over 204 bhp??
It doesnt have a 6 branch to start with and nor has the head had any work.

Just to point out that Karan's 2.7 runs unichip with a MAF conversion and that is very impressive.

Alpina C2 2.7's are a fair bit more special than most custom made 2.7's as they have custom pistons, steel cranks and very nicely flowed heads.

Getting past that 210 bhp goal post is alot harder than it seems and alot of people fail.

[Moofles]

Getting past that 210 bhp goal post is alot harder than it seems and alot of people fail.

now i'm confused! i thought you were saying how easy (or theoretically easy) it is to get hp in the 200's from an m20? or it just me

(i'm not distinguishing between 200hp which was the figure mentioned earlier, and 210hp which was the one mentioned now...)

[M5pilot]

Its easy if you know how to do it.

[M5pilot]

Totally agreed that the Cam in the Alpina is somewhat "tame" and the ECU mapping wasnt exactly the best either but then it had to be warranty freindly as you say.

The manifold wasnt great but it gave more than 2bhp! I know this as I took mine off and got it dynoed and lost a good 7 bhp bhp.

Even given these facts, get into a standard C2 2.7 and it aint no slouch.

Add a Schrick 284/272 cam to an Alpina engine and remap the ECU and the C2 is turned into a completely different beast - I bring a car to Aces now and then which has this spec and its a beast.

18bhp from just a manifold - well, this is what the results indicate and BTB arent ones for making things up. The racing dynamics manifold is known to give similar increases on a 2.5 aswell. Anything is possible!

It if much easier to break the 210bhp barrier with another engine but the M20 does have a charm about it and the way it delivers the power is very very nice. Its delivers alot of its power way before 6000rpm and gives out lots of torque low down the rev range. Though it may be old and outdated by a long way its still does the business and makes a fantastic noise.

For big power its easier and more economical to go the E36 M3 engine route.....or even the E46 M3 engine route!

[Mops]

just a thought... would TIB's make any improvement to the hp or torque on the intake side ?

[fuzzy]

what i dont understand is if your starting with 170bhp and you are getting another 18 just by changing the manifold thats only 12 bhp needed to take it up to that 200 mark. that surely cant be to hard to get with another couple of bolt on options or a remap or cams etc, at not to high a price either but like i said, i dont know much about these engines and i dont expect i ever will

[Andy335Touring]

just a thought... would TIB's make any improvement to the hp or torque on the intake side ?

Do you mean ITB's ?

[Moofles]

what i dont understand is if your starting with 170bhp and you are getting another 18 just by changing the manifold thats only 12 bhp needed to take it up to that 200 mark. that surely cant be to hard to get with another couple of bolt on options or a remap or cams etc, at not to high a price either but like i said, i dont know much about these engines and i dont expect i ever will

don't worry about it fuzzy, i think you did good to get rid tbh, if you wanted that much power...

i'm just going to wait for some damn results, lol - if it's cheap, it's cheap and so be it. just going to wait for someone else to do it first

[Chaos]

what i dont understand is if your starting with 170bhp and you are getting another 18 just by changing the manifold thats only 12 bhp needed to take it up to that 200 mark. that surely cant be to hard to get with another couple of bolt on options or a remap or cams etc, at not to high a price either but like i said, i dont know much about these engines and i dont expect i ever will

are u starting with 170bhp tho ?

from what ive been told the phase 2 325i's struggle to make over 160bhp

[Mops]

just a thought... would TIB's make any improvement to the hp or torque on the intake side ?

Do you mean ITB's ?

yeach, a typo, I meant ITB's.
here's the ITB's on m20b25 thead and pics
that's what I'm talking about - there's even a video with mean ass wound of that engine - http://img.photobucket.com/albums/v699/jonvolk/e302.jpg

whole thread here - http://www.e30tech.com/forum/viewtopic. ... tb&start=0


here's a thread about theroetical N/A m20b25 mods
http://www.e30tech.com/forum/viewtopic. ... hlight=itb

[chip-3door]

Argos, sounds like the M20 and the A series have a lot in common in terms of being very "safely" cammed and suffering from the standard manifold and headwork.

I bet the standard MAF can cope with only 20% more power, i suspect people are looking in the wrong place when they get rid of that instead of removing a bit of metal from the valve throats!

[chip-3door]

Argos, it was the throats i was referring to, not the ports, just a slight reshape just behind the valve.
But thats from memory and its quite some time since ive seen a bare M20 head.

Interesting stuff about the emissions, its funny how emissions friendly and fuel efficienct are NOT the same sometimes!

[Mops]

Interesting stuff about the emissions, its funny how emissions friendly and fuel efficienct are NOT the same sometimes!

What I cant comprehend is that the engine which runs lean might be less fuel efficent then engine that optimum (stoich) mixture.....

[chip-3door]

Interesting stuff about the emissions, its funny how emissions friendly and fuel efficienct are NOT the same sometimes!

What I cant comprehend is that the engine which runs lean might be less fuel efficent then engine that optimum (stoich) mixture.....

optimum to effiency is just a little leaner than stoich.

i would guess that to get emissions to an acceptable level they probably ran 16:1 or more at some points?

[naser]

Hi
on more modern emissions standards there are NOx limits which would make it imposible to run the car at very lean mixtures. Also running the engine on lean mixtures would result in extremely high temperatures in the cat. In most modern cars the ECU will run rich on full throttle after about 4500 rpm in order to cool the cat. Anybody know exactly what the emmisions regs were back in the early cat days? The lower comp would of course lower the exhasut gas temp and hence allow a certain amount of lean running before the cat gets damaged. But the map should be set to run lean on part throttle, normally on full throttle is could be set to run richer.

I was looking at the zone shop and there are 2 exhaust manifolds, what is the main difference in performance characteristics between these? Why the enormous price difference?

Cheers
Naser

[Gunni]

Jordan,

You do know that over the Atlantic the motronic is not a dark alley of Magic as it is in the states,
Over here their are tons of shops that can dyno tune your Motronic, relaving you of any pinging problems be it hot or cold,

You didnԚ´t specify any reason behind the decking the block,
aside from the ones you also mentioned fixes for,

"Not right" isnԚ´t an answer,
Anything that works and maintains reliabilty is just as right as anything else.

[Andy335Touring]

just a thought... would TIB's make any improvement to the hp or torque on the intake side ?

Do you mean ITB's ?

yeach, a typo, I meant ITB's.
here's the ITB's on m20b25 thead and pics
that's what I'm talking about - there's even a video with mean ass wound of that engine - http://img.photobucket.com/albums/v699/jonvolk/e302.jpg

whole thread here - http://www.e30tech.com/forum/viewtopic. ... tb&start=0


here's a thread about theroetical N/A m20b25 mods
http://www.e30tech.com/forum/viewtopic. ... hlight=itb

I've seen JonV's TB's before, some nice work there.

But in the contex of this thread(cheap 2.5 mods ?) i don't know how much power you would gain out of a standardish 2.5 ?

If you wanted to keep the M20 N/A with home made ITB's like Jon's and mega squirt then you would want a fairly lumpy cam to get engine to breath more to get the best out of the TB's.

Depending on what sort of power delivery you want then i'd guess a 288/288 for mainly road use/odd track day or if you are going to use the car a lot on track then may be go for the 304/304 cam ?

What i'd guess would happen if the throttles were over sized for the engine then the last 1/3-1/4 of throttle movement wouldn't make any more power if the engine couldn't consume/suck in all of the available air.

I was going to modify some E28 M5 TB's (6 x 45mm throttle plates) to fit my M30 but i think they are over sized for my engine unless i fit a lumpyer cam than my 284/280.

So i have decided to improve the breathing a differant way, admittedly this hasn't got a lot to do with the M20 as this mod won't fit but the M30 is very similar to the M20 but with an extra liter(ish) of capacity so my theorys might be kind of relervant scaled up/down ?

A mod i have seen on an M30 turbo relocates the standard TB to the other side of the inlet manifold so running the intake/charge pipe work is easier, this also has the benefit in N/A guise of placing the air filter and intake pipes on the cold side of the engine away from the exhaust manifold.

The flat side of the inlet manifold is roughly 95mm x 200mm so i can fit a fairly big TB to it once it has been skimmed flat. The stock TB is 64-65mm. I had a look on the US ebay site for a bigger TB(UK ebay was useless) and there was a wacking big 90mm TB but it probobly would have been to wide.

But this one should do the trick mounted virtically(sp?) with the throttle mech' on top and the TPS on the bottom. Not sure yet weather i'm going to bolt it on or have it welded on ?



Each TB is 60mm, to compare the sizes of the TB's i have worked out the total surface area in mm2 of the following TB set ups.

M30 = 3318
2 x 60mm = 5654
M5 TB's = 9542 (or nearly three times bigger than the stock M30 TB !)

This mod will hope fully compliment my existing mods(head/cam/Emerald/larger injectors) and if i ever turbo the old M30 it will be handy to have the TB located on that side of the manifold.

It's a shame theres not a nice big flat surface on the M20 manifold to do some thing similar ?

What about welding a bigger TB mounting plate on to an M20 manifold so you could use a bigger TB ?

How big is an M20 throttle ?

How about a bored out M30 TB ?

I'm not sure on the practicalities of of implimenting this idea though ?

Sorry for rambling on

Andy

[Moofles]

hey andy, what kind of hp are you hoping to get out of your m30 with those mods? is it going to give it a respectable power figure for those 3.5 litres?

[Andy335Touring]

It's about 240-250 now and i'm hoping the twin TB might give me an extra 20 ish ???

[chip-3door]

Jordan,

You do know that over the Atlantic the motronic is not a dark alley of Magic as it is in the states,
Over here their are tons of shops that can dyno tune your Motronic, relaving you of any pinging problems be it hot or cold,

You didnԚ´t specify any reason behind the decking the block,
aside from the ones you also mentioned fixes for,

"Not right" isnԚ´t an answer,
Anything that works and maintains reliabilty is just as right as anything else.

Yeah some of the lads over there with vauxhall turbos are getting crazy power figures whilst still on the motronic 2.7 ECU


I also noticed Jordan decided not to answer that, im guessing its cause he's realised since that he was wrong to say it but doesnt want to mention that? LOL

[Moofles]

It's about 240-250 now and i'm hoping the twin TB might give me an extra 20 ish ???

270 would be a reasonably nice figure for the 3.5 - i just find 218 awful! it doesn't even make a huge amount of torque (relatively huge, i know it is decent) to compensate, that's the real kick in the teeth!

how much will the mods have cost you?

[Chaos]

i just find 218 awful! it doesn't even make a huge amount of torque (relatively huge, i know it is decent) to compensate, that's the real kick in the teeth!

what do u expect from a lazily tuned engine 70's design engine.
its totally unstressed, will run to 200k, makes decent power, and has torque from nice and low down.
in a 6 series it makes for a quick car (relative for the time) and in an e30 makes for a car that in a straight line ihas the match of an e30 m3 and yet will happily lug from low revs in a high gear.