tedesco

I belive as well that the compressor is certainly on the "big" side for the 2.5 and stock rev limit. What is more the limiting factor is that to make it flow right and to reach the 25-30psi it needs quite some turbine power. This combined with the #8 housing is not ideal for my taste. Turbine/ehaust combi too small. The result is that you realy need to floor the throttle after every shift and even than wait for the boost to build up again. It is not a too small BOV but the necessety of a quite big pressure ratio over the turbine to supply enough power to drive the compressor. So the first part in the turbo that reaches the limit is the turbine that nedds a huge pressure ratio to drive the compressor. It can not spin the compressor fast enough to reach its flow capacity.
My comment from above that what I said before is not completly correct is liked to what DUKE mentioned: Even if the volumetric eff of the engine dropps it could be party compensated by the compressor running into the sweet spot or at least more efficient.
There would be more to mention because boost does not equal torque but that is all for now.

toddk911

This is my dyno (Mustang and new guys that didn't set it up right) so this is only to review the curves.

18psi STOCK head and same Super 75 turbo. Also, my chips are way off from my current setup.

So all that considered, you can still see the tq. curve holding well in the high revs.

toddk911

Also, only a 3rd gear pull.

Tq would have built more/sooner in 4th gear.

Porschefile

Sorry to bring a post back from the dead but, I had a couple questions for you George D. I was wondering if you could go into a bit more detail on what cam, intake, turbine, and hotside you were using to acheive that dyno @ 427whp and that nice flat torque curve? Personally, I'm betting that you have a #10 hotside and aftermarket cam at least but, I'm not sure about the turbine (stage 3 or 5?). Your torque curve is perfect and exactly the type of curve I'm aiming for. I'm thinking if it is a #10 hotside that that is a large part of the improved top-end torque curve. Judging by a majority of 951 dyno's I've seen, most people's torque curves tend to plummet off the face of the earth above ~5500rpm or so , which has been really worrying me for awhile as far as my high hp aspirations go. After measuring #6 and #8 housings and comparing them to conventional Garrett external gate T3 housings, it appears to me that even the #8 is pretty restrictive (for larger turbos, not smaller stuff like K26's) and a large part of the reason for the poor top-end curves so many people experience with ~350+whp 951's. Although the numbers may not be 100% correct, the best I've been able to determine is a #6 is ~.46a/r T3, #8 ~.57-.60a/r T3, and #10 ~.70a/r T3. I don't really have enough facts to back up that kind of statement, though judging by what I've seen in other communities like the DSM group, there are some striking similarities in overall power curves. Seeing your dyno has reassured me that what I'm looking for is definitely possible. Anyways, thanks for any details you can give us George.

George D

This car is pretty basic. The engine is stock with the exception of a Stage 1 Lindsey Racing head. The turbo is the LR super 75. I don't know the specifics, but they do at LR. The car is also using their stage II intercooler, 55lb injectors, MAF with mafterburner, and Max 951 chips. The car did not run nearly as well till I installed Russell's chips for this car.

The turbo is great on the top end, but laggy below 4K. Granted boost comes on prior to 4K, but it's laggy at a small track. Last month at Arroyo Seco those EVO's would catch me in the corners, then absolutely smoke them in the straights. I was amazed that they would begin to catch up in the tight corners. Corners so tight you are either at 6K in first or laggy in second. Good day for a smaller turbo. Sean's 951 with the stock K26 did much better in the tights that day.

The car runs really well. We just installed a lightened flywheel and clutch from Area 951 along with new axles. Car is tight. More money was spend on the brakes and suspension than the engine stuff.

George

RolexNJ

Why don't you find out the config on the Super 75? Maybe you could pull it and change out some things to it? I would look into that. Also, I didn't see it in the thread, but are you running the stock cam too? Sorry if you posted that info already. I will agree with you too George, the Super 75 is a big turbo and can pull all the way to redline hard. However, depending on the config, "I" found it to be laggy under 4K also even with my old 3.0L 8V, which had a ton of goddies on it too. Are the type of tracks you do more spring/short or are they longer speed ones too?

George D

We'll see about the turbo. I have the stock cam. I like having all that power above 4K. I'll wait for the variable turbos to come out before I mess with what I have. It shouldn't be too far out. As long as I can stay in second in boost in long sweepers, the car does really well. On the straights it's just a blast on race gas holding 24psi to redline. These are fast long track cars, even they are approaching 20 years old.

A variable hotside would just make everything better.

Here are the local tracks that I've driven here in AZ.

PIR Degree of banking: 11 degrees in turns 1-2; 9 degrees in turns 3-4
Degree of banking on straights: 3 degree, front; 9 degrees, back
Length of frontstretch: 2,179 feet
Length of backstretch: 1,551 feet

Firebird: Firebird Course - 1.6 Mile or 1.1 Mile Road Course which utilizes 1/4 Mile Dragstrip with up to14 turns and a 5/8 mile straight-away; used for amateur road races, testing for professional racing teams, television commercial production companies and Ride & Drive Programs.

George

Porschefile

Honestly, IMO the Super 75 is a monster turbo. With either a T4 hotside or #10 and running a Stage 5 or P-Trim turbine, it's capable of breaking 600whp. Personally, I'd like to see more 951 guys running larger hotsides (like a #10) on smaller turbos. In my experience with other cars, using turbos around the size of a Gt30r, Gt35r, LR Super 61, Super 75, etc (basically 350-600+whp turbos) really need an exhaust housing similar in size to a T3 .82a/r or larger as the larger wheel sizes would be too restricted with something smaller like a T3 .63a/r.

Basically my method of thinking is why put some 600whp capable wheels in small housings that will restrict the max power to say 500whp when you can run slightly smaller and more responsive 500whp wheels in larger housings, and ultimately have a better top-end power curve as well as an overall more responsive and less restricted turbo. Since the #8 housing is similar in size to about a T3 .60a/r housing, IMO that alone is probably the main explanation for the current state of 951 power levels (geez some people here still think 400whp on pump gas is a pipe dream ), spool times, and horrible top-end power curves.

If anyone would like, I can link you all to plenty of other dynos of various other non-951 cars with similar sized motors that show similar trends in the power curve, power numbers, etc. I see striking similarities in dynos between Srt4's, 240sx's (with turbo kits on the 2.4l and not SR swaps), WRX's, etc. Personally, I'd rather have a larger and more efficient hotside, sacrifice a few hundred rpm in the boost threshold, but have substantially increased power numbers and a significantly improved top-end curve. Sorry George, I'm not knocking on your setup (actually I like it a lot). I'm just speaking generally and hoping a few 951 guys might catch on. But what do I know since non-951 experience doesn't count and it's necessary to re-invent the wheel with these cars. j/k

RolexNJ

Well George, if you like that powerband, then that is all that matters. So forget what "anyone" says for you like the characteristics, period. But FYI, those tracks are short sprint. Anyway, glad to see you are happy with the car, the clutch, and the RWHP it makes. Enjoy it my friend.

special tool

Its not just the airflow with the 951.
These engines have a couple problems around 500 RWHP that very few people are aware of.
You cannot slap a huge turbo and big-valve head on a 951 and turn up the boost.
You will blow up so fast your head will spin.

But I am working on it.

RolexNJ

I hear you. You are one of the "very" few who has pushed the envelope out of his own pocket I might add too, to see what these cars are capable of. So my hat is of to you. To many peple think it's as easy as slapping on some mods as you stated, and it is very far from that.

Porschefile

Nice try there buddy. Who was the one telling you that without a MLS gasket and aftermarket studs (or at least new oem ones) you would see head lifting around 500-600+wtq? Yep, that was me. It's just common sense and common knowledge in most other car circles that for that kind of power out of a 4cylinder you want a metal headgasket, stronger studs, and possibly cylinder sleeves depending on the exact engine design and power level. I'd appreciate it if you'd stop talking to me like a newbie. I may not have done much in the 951 community but I have plenty of experience with modding other cars, and as I said before it's not necessary to "re-invent the wheel" to understand how to make power reliably. These cars have alusil cylinders. Oooh big F'in deal, plenty of other cars have coated cylinders and plenty of people know how to work with them. But hey, they have an open block design. Yeah, well so do Hondas and they run sleeves all the time. I could go on and on. Congrats on making the power you have, that's great. Geez, just have a little humility. Sometimes this group acts as if the only people that know anything are 951 owners with built cars. Why don't you reply when you can figure out how to keep your torque from falling off the grand canyon above 5500rpm (here's a hint, I've explained how in plenty of my previous posts).

special tool

You've explained how in theory, like always.
You will give your theory, I will give my experience.
The things you mention are the tip of the iceburg - but I guess you hadn't guessed about that yet.
And you are a newbie.

toddk911

As usual, awesome insight you have posted on this thread. Except for a few people like ST, Rolex, Tony G and now the 3.2 LiL, not many people in the 951 community really have or even want to push these cars to the limits. You take general lack of motivation with a subtle closed mindedness to other car communities (i.e. "well, I don't care if a Neon is making 600whp, it's still a Neon) this is going to be a long road to get the masses of 951 owners out there pushing their cars to even mild "limits"

Porschefile

Yet again, you completely miss the point. Ignorance is bliss, isn't it? Oh yeah, and BTW the earth isn't flat.