Look at how much torque you have at 3k and below. Looks almost 20bish. Thats an easy way to tell how fast your turbo is spooling. Go with a larger exhaust A/R to move your power peak a little higher in the power band.

https://www.rx7club.com/attachment.p...hmentid=120697


Personally your power band looks excellent for a daily driven street car.



Edit: Did a search and found Artguy's M2 ball bearing set-up that runs sequentially.

HP graph
http://www.conceptart.org/dyno/ArtguyM2hpsheet.jpg

Torque graph
http://www.conceptart.org/dyno/ArtguyM2torquesheet.jpg

WoW!

Hmmm after looking at the graphs, you may have a different problem. AMRX7 you lost over 100 hp from 7k to 8k while Artguy only lost about 40 hp in the same rpm range. I don't how if Artguy's engine is ported? I know I'm comparing too completely different setups, but you wouldn't think a single would drop off like that (especially compared to twin turbos).

Well that make a difference as opposed to running street gas.

Artguy's engine was ported, pretty good size port too from what I remember. As I recall, he later found out that that engine had poor tuning and had mediocre compression, which explains the relatively poor low-end. Perhaps Jason can chime in and set the facts straight.

In any case, that is a pretty quick drop off in the GT35 dyno above...a combination of conservative tuning, backpressure, and stock porting, perhaps?

I know I'd still be damn happy with that powerband. That sucker is rocking just above 3k rpm with a table-flat torque curve after that. For a street-driven car, that looks awesome!

that drop off at high rpm is a stock ported motor and a small turbine side, although the high rpm drop off looks a little more then usual... low end torque and boost responce looks pretty good by the dyno graph.

IIRC, it is probably still too rich on the top end. We did lean it out some on subsequent runs, and it picked up about 20 ft-lbs at 8000rpm, but there was no change until after 7500rpm.

Thanks for the responses. I'm just trying to figure out what to do next. I like the response of the small turbine, but would like to extend the powerband out just a bit and make more like 400-420whp. Sounds like porting may help, and I want to build the motor properly instead of relying on a stock reman anyway. If that doesn't do it, upgrading the turbo is easy.

-Andy

Resurrecting old thread with some updates. Since this thread originally started I at one point had the motor ported (good sized street port), and just recently stepped up the turbine housing to 1.06 A/R. Need to get all the dyno plots in one place, but basically with my T3 GT35R setup and....

stock motor w/.82 A/R turbine at 15-16psi
-about 375whp
-hit full boost around 3700rpm (need to go check that number)

large street port motor w/.82 A/R turbine at 15-16psi
-about 400whp (and much more on the top end, about 80hp more than stock ported motor where it would fall off)
-full boost by 3800rpm

large street port motor w/1.06 A/R turbine at ~16psi (boost control was hard on this dyno, small roller dynojet)
-about 410whp
-full boost by 4200rpm

The power gains with the porting were very noticeable especially on the top end. Spool and low end torque wasn't quite as nice, but net was much more power in the 7Krpm+ range.

I was *hoping* the larger A/R turbine might be what the system now wanted, but was disappointed with results. Spool obviously suffered by about 400rpm, and top end power was almost the same. Since this is an autox only car, I will probably go back to the smaller .82 turbine.

-Andy

In Kyle's car (Nocab72...Turbo Magazine article) we were only able to get into the 460's at 17psi before we started hitting a wall. Same turbo with T3 (1.06AR Turbine) but on LARGE street ports. How "LARGE" we don't know since the engine has not given a hint of needing to be torn down (not driven very much).

I don't have a dyno chart from that session handy but I remember the same general shape of the curve...maybe without as much of a drop as with your .82AR.

I will have to side with our Aussie friend here and state that in tuning cars you have to keep in mind the whole car. I wouldn't call someone ignorant over anything, but everyone on this thread has been wrong before...and will again. It's nice to see people sharing information and debating in a civilized manner. Adding to the general knowledge pool.

Tony

Yes, I wasn't too happy with the larger 1.06 housing. I expected to lose some spool, but was hoping to see more top end gain. The spool loss was large IMO, and the top end gain was almost negligible. There were some dyno-dyno differences here and to get a perfect picture I need to go back to the same dyno to confirm.


In any case I was concluding that my restriction is somewhere else in the system. A few things I can think of...

-port job isn't that large
-manifold design --- it has short runners (about 4.5" long)
-wastegate plumbing --- they route back into the downpipe about 16" from turbo outlet, but at 90deg angle (obviously not good for flow)

-Andy

Another possible restriction is the intercooler. I'm using a Spearco core that is rated at 470hp and 700cfm. I might be maxing it out by 8000rpm or less on the cfm. If the hp number is crank hp that would make sense too since I seem to have trouble getting much past 400whp.

-Andy

Andy,
Why are you trying to make my job harder. We've been having a nice "even" fight lately. Trust me, you can't use much over 400hp. ;-)

Haha, I know Erik especially at HPT where it is hard enough to use 300whp. We need an RX-7 AWD kit.

In any case I think I am done in the power dept for awhile. I have a very responsive 400whp setup now and to make significant power gains would probably mean new I/C and all new manifold and exhaust (and maybe turbo and maybe port job...;-) ).


-Andy