E30 Zone

would it be posible to run e36 m3 throttle bodys on a m20 and if so what sort of work would be involved and would it be worth while doin it

not worth it

only worth it if you intend to run close to or more than 250bhp.

not worth it !!!

ITB's are great until you sit down and calculate the induction harmonics, runner lengths, etc. I seriously looked at building or buying an ITB setup for my race car, however I calculated we needed something like 500mm runners. VERY hard in an E30 engine bay on an M20 (particularly if you run an air flow meter).

We are going to stay with the standard intake plenum (albeit bored out a fair bit), and a BBTB. Look at the runner length on the factory M20 manifold. They are fantastic. Equal length and very long (some 550mm long). It would be very hard to improve at a reasonable cost.

you could ditch the afm and go Alpha N on the motronic
it can be done !!

fowler wrote:you could ditch the afm and go Alpha N on the motronic
it can be done !!

Empty wallet time $$$

It doesn´t have to cost anything substantial.

It can be done on the stock ecu.

Gunni wrote:It doesn´t have to cost anything substantial.

It can be done on the stock ecu.

yes it can so not to bad on the pennies sounds fricking awesome to

Done it once and would not spend the money to do it again





Jason

are those m3 bodies or bike ones? the change in port shape over such a short distance is horrible.

They are 36 m3 3.0 ones and theres not that much room to make a longer transform.

I think a webber manifold and a set of jenvy dcoe throttle bodies only would of been £150 more and at the end of the day and be quicker/easier to install

Doing it again I would use bike TB's as the port transition is easier (Which reminds me I have a set of bike itb's spaced out for an m20 in the shed)

Jason

hmm, guess great mind think alike.....

looking at using the stubs from an m20 manifold ground out to match the ports on one of my heads with some tube added for length, bike boddies on the end with trumpets into an airbox.

that or the same without the boddies and a large singe body on the end, same effect in the long run.

How do you go clearing the brake booster?

I was going to buy a M20 DCOE manifold from Rowland Manifolds, and fit "EFI" DCOE throttle bodies ("EFI" are an Australian throttle body manufacturer like Jenvey, AT, TWM, etc...). I have read too many bad stories about people trying to fit bike carbies, and not being able to tune them properly.

Ideally running ITB's with an Alpha N setup would the go, as you do not need the bulky air box. Unfortunately, despite the world wide interest, no one appears to have yet developed a simple, effective bolt on ITB setup for an M20. What does that tell you?

what restictions to you have on your race car as i woul;d say use alpha N as it will totally change the car drive.
Not a fan of Tb's to be honest but when they are on they do sound nice..
as i am sure there will be a 2.7 on Tb's coming up for sale soon

Diblas have been selling a bolt on kit for years, what it tells you is that is not a cost effective mod unless you have done a lot of engine work to get the benifit.

Also several uk track/race car runs webers with the stock brake boosters okay

Jason

MillRat, I have seen you comment a number of time in various threads about induction harmonics. It's apparent that you have put some effort into designing your own runners. I designed my own inlet manifold for my Toyota 3SGTE engine following the same theory, calculating the resonant frequency as a function of the runner length and diameter.

The reason I mention this is because I always understood that throttle bodies are an advantage to a track-car by virtue of the fact that they are short and fat. In essence, they push the peak of the torque curve up to high RPM (at the expense of torque at lower RPM. Since power is the product of torque and RPM it pays to shift torque to a higher engine speed since this equates to more power, and driving around the track revving the nuts off the car is of no particular consequence (unlike a road car) so long as the engine lasts the duration of the race and, as Jason pointed out, has had the necessary work done to it to ensure that the benefits are fully realised. A daily-driver that has had its peak torque shifted upwards just wouldn't make much sense to me, especially if it struggles to reach sufficiently high RPM to realise the benefit in the first place.

Yes, the multiple throttles certainly aid in increasing the overall VE of the engine, but the major draw card (as I understand it) is not the butterfly valves themselves, but the shape and size of the throttle bodies. To my mind, adding lengthy runners to throttle bodies somewhat negates this.

BTW, Since my track car is turbocharged I deliberately increased the length of my runners in order to improve torque at low RPM where it is typically lacking on a low compression turbo engine. The reduced VE at higher RPM (due to the longer runners) is more than compensated for by the turbocharger. I applied the same theory to the design of my exhaust manifold, except I worked with a faster speed of sound through the exhaust gas due to the fact that it is substantially hotter than the inducted air.

I love ITB's and all the theory behind them.

Jason, I believe you with Webers, but I was thinking more with respect to the airbox.

Geoff, great comments as always.

I guess my line of though at the moment is that most old school race engines I have seen (3.0 CSL as an example), run really long trumpet runners. Was this purely to boost low down torque (hardly seems likely for a full race engine). It certainly is a complicated science, and is no wonder car manufactures dump huge volumes of money into developing induction systems.

I run triple side draft carbies on my M20 E21, and with respect to throttle response, it is better than my race car. Unfortunately my E21 engine is basically stock internally, making it impossible to compare the 2 engines in any other way.

I came to the conclusion that if I was to build an ITB setup (that fit, and were effective) I would need to fit an adjustable cam gear, and a very large cam (+300) to realise the true benefit (on top of all the work that has already been done to the engine).

Induction harmonics are indeed complex.

American V8 owners realize better drivability, startup, cruise, power with ITB´s. Some of their carb manifolds are so bad that they would just not work with injection as each cylinder is so mis-fed vs the other ones that it runs very rich or lean. A carb handles that as the air going in to a cylinder will pickup the required fuel on the way in. More air, more fuel goes with it.

There is some talk about ITB´s on R3vlimited by a user called rs4pro who had ITB´s on his.

Gunni wrote:Some of their carb manifolds are so bad that they would just not work with injection as each cylinder is so mis-fed vs the other ones that it runs very rich or lean.

An AFM on each cylinder

WOW! What an interesing thread (But well over my head!)

Slightly Off topic, is the longer length of the inlet manifold tubes on an M20 eta responsible in part for the less peak power and more torque vs a normal M20?

Andy

Andy325i wrote:WOW! What an interesing thread (But well over my head!)

Slightly Off topic, is the longer length of the inlet manifold tubes on an M20 eta responsible in part for the less peak power and more torque vs a normal M20?

Andy

Possibly. Looking at Geoff's post, it would suggest that it may be contributing (I am not saying Geoff is right, but he is rarely wrong). I was never aware that the eta plenum was different.

There you go, learn something every day.

GeoffBob wrote:

Gunni wrote:Some of their carb manifolds are so bad that they would just not work with injection as each cylinder is so mis-fed vs the other ones that it runs very rich or lean.

An AFM on each cylinder

now that is a GREAT idea

MillRat wrote:I guess my line of though at the moment is that most old school race engines I have seen (3.0 CSL as an example), run really long trumpet runners. Was this purely to boost low down torque (hardly seems likely for a full race engine). It certainly is a complicated science, and is no wonder car manufactures dump huge volumes of money into developing induction systems.

The trumpets come before the throttle valve on an ITB, whereas the runners always come after (such as in the case of a standard intake manifold with throttle valve, plenum chamber, and then runners). So far as I am aware (I'll have to look this up to confirm) the trumpet that precedes the throttle on an ITB is there to promote laminar (non turbulent) air flow into the engine, whereas any length of pipe (runner) that comes after the throttle is there to dictate (in part) the torque curve.

Trumpets (if memory serves) work as follows: the mass-flow (kg/sec) of air being inducted through a trumpet is identical at any given point along the length of the trumpet (Think of it as a garden-hose where the amount of water going in from the tap has to be the same as that coming out of the sprinkler. However, because the trumpet is flared (has a larger diameter at its opening than at its interface with the throttle) the actual particle velocity of the air on the flared end is slower than at the narrower throttle end (that is to say the velocity of the air must speed up as it progresses from the fat to thin end of the trumpet.

Because of this the air entering the trumpet sees a slow and progressive transition from standstill to fast. This avoids the condition (such as would be the case if an inlet manifold for ITB's were omitted altogether) where the air would have to transition from standstill to fast almost instantaneously, and would thus become highly turbulent. It would literally be like trying to suck a cyclone down into the engine.

Trumpets are, therefore, a form of impedance matching. Generally, the longer and fatter the better to make the transition from slow to fast moving air as gradual as possible. Unfortunately space does not always allow for long trumpets on ITB's.

Okay, that makes sense. Your logic also explains why those old race engine I was referring to often have very long trumpets, but have the throttle body (often a slide type) bolted to, or very close to the head.



And

More (sorry I just love these setups...... One day, one day.....)

MillRat wrote:Okay, that makes sense. Your logic also explains why those old race engine I was referring to often have very long trumpets, but have the throttle body (often a slide type) bolted to, or very close to the head.

Exactly

Beautiful pictures BTW, total car porn

its quite nice to see sensible comments on throttles for once, you all right that most throttle setups are no good for a road car, far to large and short.

the trumpet works exactly as said above, the intention is to stop the air going turbulent as it enters the body, one other thing it does is stop the air having to turn 90 degrees as it enters the throttle, which is why we stick a bell mouth onto the head when flow testing.

the advantage of the throttles is an uninterrupted adequate airflow to each cylinder. with throttles theres no charge scavenging between cylinders and you have the option of sizing them correctly to give the flow you need.
that dosent mean bigger is better though, go too big and you will lose the air velocity into the cylinder, which will end up reducing the power at road speeds as the cylinder filling will be lower. the other problem with bigger is you will lose your throttle modulation, as a small angle of the throttles is a large increase in airflow compared to the large single body.

the intake pulse will be traveling from the back of the valve to the throttle plate, and with each bounce forth and back the pulse will get weaker.
the pulse travels at the local speed of sound, which depends on the air temp and the local air pressure, so its quite easy to calculate the distance the pulse travels in a second or how far it will get in degree of rotation of the engine.
thus making it possible to calculate the length needed in order to catch the pulse when the intake valve is next open.

ill do some maths on it in a minute and post up the results, then copy some of this to the 2.8 thread.