Another step forward for the Triple-T twin turbo

Herr-Kuhn · 07-04-2007, 10:40 AM

This weekend I will be in Florida to lend some assistance to the Triple-T. We are going to upgrade the camshafts and intake runners in the hopes of getting some more mod range and top end out of the car. The 79 cams are a nice upgrade over the 84 cams...the 84s have decent lift, but a low duration. I think we are getting about 10 to 12 more degrees of duration by stepping back to the 79 cams.

Those who have followed this build know that we used the Euro heads, 84 US cams and US intake runners, thus there is a mismatch between the heads and the intake runners. Mark has sourced some Euro runners we are going to try and use on the car. I believe the cams will make the biggest improvement...my guess is another 20-30 HP without adding more boost, but time will tell.

This car has already posted 450 ft-lbs RWTQ and 400 RWHP on just 10psi. This is a 4.7 liter engine and is still on Reeve's manifolds and IHI turbos.

Once I get home and get settled I am going to do some more tuning on the 32V car. It will be interesting to see how the Triple-T compares to the 32V car since it has been so long since I have driven the Triple-T. I know the 32V car can make a new M3 look like childs play, even from a standstill. That was one UNHAPPY M3 driver...that paddle shifter is fast, but it can't cover for 500+ ft-lbs of torque

Danglerb · 07-04-2007, 11:21 AM

Whats the US vs Euro runner ID, is it something like 1.6" vs 1.8", it wasn't that much as I recall.

sonett3 · 07-04-2007, 01:18 PM

The runners are 2.0mm bigger than the us runers.This car i think will be about 450 to 465 rwhp but time will tell.

Herr-Kuhn · 07-04-2007, 06:13 PM

Not sure on the runners, but to have them match the heads will be better than what we have now. The cams will be the biggest bang for the buck on this car for sure. It's a good step in the right direction.

mtelliott · 07-05-2007, 06:46 AM

Can the transmission hold that HP or have you done upgrades? I apologize that I haven't followed the story. I'm new to the 928 side.

Michael

Herr-Kuhn · 07-05-2007, 08:39 AM

Tranny is no issue at these power levels...and the twin clutch is quite strong as well. We're talking just brushing 500 HP here and a little over 500 ft-lbs on torque.

I'm sure this engine can churn out a lot more power with better manifolding and turbos too!

Herr-Kuhn · 07-05-2007, 05:07 PM

It looks like we'll be able to install the Euro plenum, runners and 79 camshafts into the car. The throttle body will take more work to pull off and I don't have time for it this weekend.

Fabio421 · 07-06-2007, 07:23 AM

Is there something special about the install of the throttle body? If so, send Mark and I the details and it shouldn't be a problem. I get back into town in a few days. I'll be glad to help. This car is going to be a real sleeper when its finished. It already pulled like crazy before the cam and runner change. And the fueling wasn't even finished. I suppose we will have to add some more fuel across the board now that its opened up a little more. This is a really cool project.

One small step for Kuhn Performance, one giant leap for OB's.

sonett3 · 07-06-2007, 01:34 PM

It has to do with how the callaway feed pipe feeds into the U-pipe below the throttle body. We are going to try and fit the throttle body to the system tonight. He already has the top side torn down and we may even get the camshafts harvested tonight...a lot easier without the runners on the engine.

I'm still waiting to get some spare time on the 32V car...my chores are nearly completed in KY...shrubs, landscaping, etc...too much stuff to do and not enough time to do it.

sonett3 · 07-07-2007, 01:49 PM

The cams have been harvested and replaced...here is a shot of the two cams side by side.

Here we have the situation where the cams have the same lift on both the exhaust and the intake, but the duration on the 79 cams is much greater than that of the 84 US cams. If you look closely you can see how the 84 US cams have a sharper peak on the lobes, where the 79 cams have a more rounded look...this is due to the short duration on the 84 cams. I beleive the 79 cams to be the best cams out of all of the stock 16V cams for turbocharged use. The 80-84 US cams are emissions cams...they are really bad for top end power because of the shorter duration and the 80-82 have crap for lift and duration.

I'm certain these cams will work well. I had forgotten what a PITA changing cams on these cars was...I hate that job as it is very time consuming. Add in 90F and 80% RH here in Florida and you can get tired out in a hurry. I head back home tomorrow mid day, but I think it is hot there too!

We have decided to use the Euro runners and plenum on the car. The throttle body will not fit with the existing forced induction parts without major re-work.

Herr-Kuhn

Danglerb · 07-07-2007, 02:42 PM

This pict is from I think a 79 Euro, is it a larger size, but maybe different hookup?

Normy · 07-08-2007, 04:13 PM

Herr Kuhn-

I'm a bit perplexed. I understood that turbocharged engines really preferred camshafts with less duration.

-Turbochargers are devices that respond quickest when they are subjected to high exhaust pressures. When an engine is low in a gear and the throttle is wide open ("overboost"), the exhaust stream is very highly pressurized and the turbo rpm is higher relative to the crankshaft rpm, which simply means that the turbo spools quicker. Camshafts with short duration and lower lift tend to favor low-rpm power, so they usually make a turbocharged engine seem more powerful. No?

You are putting '79 cams in a turbocharged engine; they have far longer duration than the '84 stock US emission cams- this seems backwards. What's more...if the "hotter" '79 cams are better...then why not go all the way and find a pair of '84-'86 S2 cams and try those instead?

Keep up the good work!

N!

sonett3 · 07-08-2007, 04:52 PM

84-86 S2 cams have way to much overlap.

Herr-Kuhn · 07-09-2007, 07:57 AM

The issue is the amount of overlap. You can always afford some, but there is a limit. From experience I know the 79 cams work really well. I picked up a bunch of mid range and upper end on my Callaway engine by installing these. The 80-84 cams are very conservative but don't flow real well above 5K. From an overlap standpoint they are perfect for TC use, but the duration is terrible compared to the others.

The Euro cams have a good bit of overlap in them. Since this car runs a log manifold setup, the back pressure can cause reversion into the chambers if the overlap is too great. We took the safe bet on the cam change.

It's all a balancing act. I actually lost nothing anywhere on the callaway engine by installing the older camshafts...it was a win-win.