M20 throttle body upgrade

[briansjacobs]

just curious what people have tried to do remaining single throttle body to get more air in. You can not bore the stock throttle body and keep the butterfly, so what to do? I was thinking about trying to adapt a 740i throttle body and boring the manifold, but I have not even lined them up yet to see if it is feasable.

my 2.8 M20 is running out of air around 6000 RPM, the torque drops out at 5300 and the HP will pull it up to 6300 but need more air to get to 7000 rpm, let me tell you 4000 trackable RPMS would be sick!

[Danny]

m30 butterfly

[briansjacobs]

does that work, or is it a guess.

[Danny]

Been done before.

[briansjacobs]

well I guess I know what im gonna do. thanks for the input, and much easier than messing with that 740 part, I think. maybe try both.

[nando]

I had one bored out to accept a 65mm TB plate (M30 size). Got it from bottlecape30 (on E30tech). The work itself was pretty good, he even smoothed out the shaft and did some work on the plate, but the TB was pretty dirty when I got it back. It's okay, I've taken it apart to have it blasted and maybe powdercoated anyway. If you didn't care what it looked like you could just clean it off and throw it on, but I'm picky. :p

you'll also need to match the port on the manifold to the TB, and it'd be a good idea to gasket match the intake to the head (the outlets of the stock manifold are quite poorly cast).

it should make a difference, I pull a lot of vacuum past peak torque (10kpa on average), even with no air filter. I'm wanting to have it all together this month. TB is being cleaned right now, dropping the manifold and TB off at the powdercoater either today or tomorrow. :)

[briansjacobs]

how much was it and do you have an email for him, no sense is reinventing the wheel if he is already profecient with the mod. Could care less what it looks like as this is track only, and car kinda looks like a war zone anyways

[nando]

I think $150? yeah he's done a ton of them. Definitely clean it before using it, there were some leftover metal shavings in mine.

you want this dude:

http://www.e30tech.com/forum/member.php?find=lastposter&t=92443

[jlevie]

The limiting factor, assuming an I head, intake and throttle body is the head. Not the intake or throttle body. To make power up top, the head needs to be modified to increase flow and the cam needs to be changed to one that will shift the torque peak higher.

[nando]

The limiting factor, assuming an I head, intake and throttle body is the head. Not the intake or throttle body. To make power up top, the head needs to be modified to increase flow and the cam needs to be changed to one that will shift the torque peak higher.

we aren't talking about stock engines here...



note the MAP value. ambient is 101.1kpa (I live at sea level). The engine is pulling ~12kpa of vacuum at 7200rpm, instead of seeing atmostpheric pressure. The filter is about 2-4kpa of that, the rest of the pressure drop is coming from the stock TB and manifold. That's approximately a 10% restriction - 10% more air is a big deal.

[briansjacobs]

The limiting factor, assuming an I head, intake and throttle body is the head. Not the intake or throttle body. To make power up top, the head needs to be modified to increase flow and the cam needs to be changed to one that will shift the torque peak higher.

524td crank, 10.5:1 compression,vac cam gear, schrick 288,miller maf and chip, port polish and valve job by extreme heads. im thinking only left is the throttle body

[jlevie]

Fair enough...

What do the torque and A/F ratio curves look like?

[nando]

Fair enough...

What do the torque and A/F ratio curves look like?

I know you were talking to brian, but if you look at the green GVE curve, it approximates my torque curve.

[briansjacobs]

I have a miller chip so I can tune it to a degree, my AFR is between 12.3 and 12.8 at WOT pretty much across the power band. The torque starts at 2500RMP and goes to 5300RPM before it starts to fall, Car is never below 3000 rpm at the slowest corner of any track I go to (the hairpin at Homestead I go thru at neutral throttle and by time the car is turned we are down to 3000 rpm which is great torque)

[jlevie]

If the A/F ratio is going leaner at the top (as suggested by your most recent post), the engine isn't running out of air at the top end in the current tune. What I'd really like to see are the curves.