Looking for upgrade to M20 Throttle Body....

[JiXer]

I am building a 3.2L M20 and really want to open up the throttle and intake.
I got an M30 throttle body, but was really surprised to see how little of a difference there was between the M20 and M30.

The 24V TB's are set up sorta different and would take too much modification to make them work, so I am looking for ANYTHING that will work.

Maybe something from a Porsche or something??? I don't know.
Any ideas out there?

Also, if I were to end up modifying something like an s52 TB, I would need to build an extension tube between the TB and the manifold which would really change the flow on the downstream side of the TB, but I don't know if that would be good or bad? Is there any engineers out there with some fluid dynamics backgrounds?

J.

[kendogg]

I have a feeling the TB won't be a restriction. Please do a before/after dyno with the TB being the ONLY change.

[JiXer]

If I'm able to do it, it will likely end up with an intake that cant really go back and forth.
I'm reading a bunch of stuff on flow dynamics and I don't think that raw numbers will be what I experience a change with. It may be more of a power band and throttle response thing.
Still reading. This isn't something I have a lot of experience with, so we'll see.

But the head is full ported and blown out and I will be running full length headers and a 3" exhaust, so I just don't want to choke the system down up front. I know a pulse tuned intake would be the way to go, but they are pricey.

J.

[kendogg]

You'll lose a bunch of torque with a 3" exhaust on an NA motor.

Seriously. Get the car complete. Dyno the car with the stock intake/TB. Then put your contraption on it. Dyno again. I guarantee you'll dyno the same, and have less throttle control. The TB isn't a restriction.

Unless you have an engineering background and are fluent with fluid dynamics and have a good bit of flow data - chances are, it'll be a losing battle.

Hell, look at the BBTB's for S52's. Even with full bolt-on's, it does nothing but muck-up the air flow. 0 whp, 0 wtq.

[JiXer]

You'll lose a bunch of torque with a 3" exhaust on an NA motor.

Seriously. Get the car complete. Dyno the car with the stock intake/TB. Then put your contraption on it. Dyno again. I guarantee you'll dyno the same, and have less throttle control. The TB isn't a restriction.

Unless you have an engineering background and are fluent with fluid dynamics and have a good bit of flow data - chances are, it'll be a losing battle.

Hell, look at the BBTB's for S52's. Even with full bolt-on's, it does nothing but muck-up the air flow. 0 whp, 0 wtq.

You may have missed the fact that I am building a 3.2L M20. This is far from a stock set up and a 3" exhaust is nothing short of absolutely necessary and I will not lose any torque. (In fact, my buddy has been experimenting with 3" exhausts on stock M20's on his Mustang dyno and with a chip and properly adjusted valves, he has actually not seen any loss in torque between 2.5" and 3" exhausts. Just slightly more HP near red-line as the only change) The S52 crank makes the M20 a torque beast. I've worked on one and driven it and I know how the power band works with an M30 TB. Its horse power I'm concerned with, not torque.

Anyway, we're getting off topic a little. Just looking for a TB solution that will allow me to open the manifold at least 4mm.

J.

[Jordan325iC]

Not sure if this is what you're looking for, but this site sells "big bore" m20 TBs:

http://blog.360.yahoo.com/blog-vNlZ8_A8dLRNzv3EnDaTz2I0HuG4NsFVdQ--?cq=1

[jlevie]

Its horse power I'm concerned with, not torque.

I don't mean to sound condescending, but you need to do some more reading. It is torque (and rpm) that you are concerned with.

I pretty sure that the limiting factor in mass flow through this engine is going to be the valves. And my intuition says that the M20 TB is probably good enough.

[JiXer]

I don't mean to sound condescending, but you need to do some more reading. It is torque (and rpm) that you are concerned with.

I pretty sure that the limiting factor in mass flow through this engine is going to be the valves. And my intuition says that the M20 TB is probably good enough.

You don't sound condescending. I'm not afraid of discussion and debate, afterall, thats what this site is for. But I didn't go in to a lot of specifics because I didn't want this to be an engine dynamics debate.

The head and the is as wide open as it can get and is not the issue here. But with a long stroke motor, there is concern of keeping the intake air velocity and capacity as high as possible so the HP at high revs doesn't suffer because the long stroke takes so long to fill the cylinder.

There are port tuned manifolds that are tuned to form the pressure wave so that the valve has positive pressure behind it when it opens. That manifold is $2,500. So this issue has been addressed, but the cost is too prohibitive for me.

Therefore, I just want to open the intake and TB a bit. The upstream intake will also be optimized to maintain velocity.

J.

[jlevie]

I realize that you've opened up the head passages, but what I was referring to is the passage formed by the open valve as being the limiting factor. The valve doesn't open all that much and thus the flow area is limited, not to mention being highly turbulent because of the almost 90deg turn the air has to take. Note that all later BMW I6 engines have a 24V head to raise this limit.

After the valves, I suspect the intake is the next limiting factor. Those are pretty long runs and there'll be a good bit of frictional losses at higher velocities. The intake is a tuned system, but I suspect it was optimized for midrange performance rather than peak power to make the car more "drivable".

[SpecM]

The S52 crank makes the M20 a torque beast.
J.

-but it doesn't make the s52 a torque beast? Why would a biger TB effect the m20 any different?

[robmespeedy]

interesting!

[Kingb]

interesting!

Whats more interesting is your pic. I have never seen this before on this site. OMG what happened???? The FPR? I saw someone on here had an engine fire and was replacing the wiring but was it you or what???

[robmespeedy]

my car was to low and i ran over some huge rock... busted the fuel line. and ... pow!

[SpecM]

my car was to low and i ran over some huge rock... busted the fuel line. and ... pow!

holy crap I never saw that second pic beofre

[z31maniac]

You don't sound condescending. I'm not afraid of discussion and debate, afterall, thats what this site is for. But I didn't go in to a lot of specifics because I didn't want this to be an engine dynamics debate.

The head and the is as wide open as it can get and is not the issue here. But with a long stroke motor, there is concern of keeping the intake air velocity and capacity as high as possible so the HP at high revs doesn't suffer because the long stroke takes so long to fill the cylinder.

There are port tuned manifolds that are tuned to form the pressure wave so that the valve has positive pressure behind it when it opens. That manifold is $2,500. So this issue has been addressed, but the cost is too prohibitive for me.

Therefore, I just want to open the intake and TB a bit. The upstream intake will also be optimized to maintain velocity.

J.

I thought Metric Mechanic sold an intake manifodl like that for around $1200-1300 (still very pricey)

Korman has an oversized TB advertised on their price sheet for around $375 + core I believe.