Ski

I ordered a big bore throttle body a couple of days ago,,,I needed to add a little more air to the mix midrange. I had a great A/F curve from 5000 to 6000(12.1 -12.6) but the 3800 to 4800 could have been cleaned up a little bit; it didn't need a lot but for $300 I thought I would try the BBTB.

Got it today, installed today, and so far so good. The first run the WBO2 went lean too fast, fuel pressure too low. Added about 6psi over two adjustments to the fuel and:
boost hit maybe a little sooner, 3600-3700 rather than 3800-4000, A/F hit 11.4 but then stabilized at 11.8 until 5000 - it was 12.0-12.1 there, then by 6000 it was 12.5-12.6. This was running 17psi, fuel pressure at idle was 36psi byt the end of the runs. This was coupled to Danno's latest chip version of his K27 chip - MANY THANKS DANNO!! I made two small increases in fuel pressure as stated above, started out at 32psi.

So maybe if your a bit rich mid range on boost, need a TAD bit more air, maybe a BBTB will help out. It won't take you from 10.5 to 12.0, but if your after say .3-.4 on you mixture, maybe it will "lean" you a hand. Worth the $$,,,hmmm,,,I guess so for now. BTW, I think they took maybe 1 to 1.2mm off of the opening, took a bit off the sides, then polished the inside.

PorscheG96

What size is the new throttle? How about the diameter of your intercooler pipes?

Ski

I didn't have a pair of calipers to do that with. I based the increase on what was cut from the original one by the amount that was taken off, measuring the difference in the upper area where the idle adjustment screw is. You know, I'd have to measure the pipes, Lindsey Intake system, I think 2.25.

fast951

If you get a chance to dyno your car, compare your output between stock vs. big TB. You'll be surprised.

dmoffitt

i've always heard/read TB is like the last thing or 2nd to last thing on the list of 951 upgrades.... can someone please prove me wrong / enlighten me as to why it's such a vast improvement, stock one seems rather sizeable as it is.

PorscheG96

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by dmoffitt:
<strong>can someone please prove me wrong / enlighten me as to why it's such a vast improvement, stock one seems rather sizeable as it is.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I'm a skeptic myself.

Seems to me the intake system between your turbo exducer and intake manifold should be a uniform diameter. Since the stock piping diameter is 2.25", the throttle opening is 2.25", and the intake plenum is 2.25" which then becomes smaller in the runners to maintain charge pressure and velocity, I can't see why a larger throttle would do anything but disrupt charge flow [turbulence].

A larger throttle would help if you have a 2.5" turbo exducer, 2.5" piping, larger intake manifold, or any intake diameter for that matter as long as it's all uniform.

Ski

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by dmoffitt:
<strong>i've always heard/read TB is like the last thing or 2nd to last thing on the list of 951 upgrades.... </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Me too. Like I said, it was just to see if I could get a touch more air and clean up the midrange of boost just a bit. I'm pretty pleased with the results, Danno's latest chip and the throttle body, still running factory electronics. Called the dyno shop yesterday afternoon and wouldn't you know it, they're waiting on some new cylinder(s) that raise and lower the plate between the drums. Maybe by Thursday.

David Floyd

Brett, is this an aftermarket TB or did you have the stock unit bored ?

When I was doing my rebuild I had the stock TB bored, not sure how much improvement (if any) it made, just thought it was one more piece of the HP puzzle.

Ski

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by fast951:
<strong>If you get a chance to dyno your car, compare your output between stock vs. big TB. You'll be surprised.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">John will that surprise be "not any gain" or " you'll be very pleased", because I have no idea with the exception that if it helped clean up the A/F curve you might get a bit more power.

fast951

Probably not any gain. Actually you might have lost HP in a few areas.

Ski

David, yeah I bought a spare and had it bored and polished.

TonyG

I gained 18HP and 23TQ with my ported intake and enlarged throttle body and have the dyno sheets to prove it.

Not needed for a stock or mildly modified car, but it's certainly something to do after you have finished all the main modifications.

I've never lost HP with an enlarged throttle body. The amount of enlarging is pretty trivial compared to some other larger aftermarket throttle bodies for other vehicles.

TonyG

Also, it's been proven that intake modifications, even on a turbo charged car, are effective.

The John Milledge 4 barrel valve intake produces an additional 30HP (although a very expensive 30HP for sure...).

My modified intake/throttle body produced 18HP.

And I'm sure my individual throttle butterfly intake will produce the additional power closer to that of the Milledge intake.

TonyG

Concerning the intercooler pipe diameter comments...

Seems to me the intake system between your turbo exducer and intake manifold should be a uniform diameter. Since the stock piping diameter is 2.25", the throttle opening is 2.25", and the intake plenum is 2.25" which then becomes smaller in the runners to maintain charge pressure and velocity, I can't see why a larger throttle would do anything but disrupt charge flow [turbulence].

I'm no expert here, but it would seem that Porsche engineers disagreed with this logic.

If you measure the outlet of the turbo it's not even 2". I just measured the Kokeln Club Sport turbo from Lindsey Racing and the ID was 1 13/16". Yet the stock piping is 2 1/4" (the pipe is paper thin too.. so the ID is extremely close to the OD).

So if Porsche engineers saw fit to install intercooler pipes, and a throttle blade that were substantially larger than that of the ID of the turbo outlet, it must mean something...