miaplaya, we have some pictures at www.bouldernissanmotorsports.com but i will post some more pictures in a new thread in the next few days.

 

gq, we datalogged through profec on our pulls and the boost controller did a pretty good job of holding boost.we can continue to adjust gain, but i dont believe it will change the curves that much. we have also adjusted rpm offset to try to maintain boost levels. the springs seem to hold good(no seep) because we could continue to increase boost.jason

 

so when you logged the boost with your Profec, where did it peak...and did it stay steady after it peaked....particularly beyond 4500rpm? If your boost pressure peaked at, for instance, 4000rpm at 22psi, and stays constant at 22psi, you should be making more power as your RPM's increase so long as your AF is relatively stable...which yours is. Even if the turbo was less efficient at 22psi than at 18psi, you still shouldnt see that dropoff in power....just less of increase across the board.

The only thing I can think of is heat soak?? Try again on another day and see what happens.

 

Oh, and fuggedabout the RPM offset feature. Disable that....

Then just learn the boost via auto mode. The idea is to have as natural a progression of boost until it peaks...then constant level after it hits it peak point. If the auto mode is set correctly, it should stabalize your boost at the desire level, once it hits the peak.

So like in my previous example, lets say your boost peaks at 22psi at 4500rpm....you want the profec to stablize the boost at that level all the way to redline.

 

good work.

our engine will be going in soon, we have done all the head work with the same cams as you... so we will see if all the port work and the oversize valves help out the high RPM power. A better intake manifold would help im sure too. We are looking into this but it will not be apart of the new motor from the start.

Are you still using the E-Manage I assume?

-Charles

 

Those turbos can easily push 25psi...peak efficiency is way above 19psi. You have a bottleneck or a leak. I'd say headwork would net you some decent gains....it may not make a big difference on a NA Z car, but one pushing the volume of air you are will certasinly benefit from it.

--wes

 

He speaketh the truth.Port and polish

 

Im not an expert, but I agree with some of the other people that mentioned headwork. Bigger valves and port and polish would probably net some good results. Also, I don't know too much about the JWT cams, but are the ground for FI or mild NA? If they are NA cams then some good turbo cams would also be very helpful.

 

BLDR, I wanted to say thank you for sharing your findings. I never even considered that at some point...the obstruction on this car would be the head! So unless you uncover something else, it appears that 22-24psi is the top range for this car....regardless of turbo design. Sounds like the head and intake manifold may be the blockage.

I would even bother swaping or rebuilding the turbos, becuase as mentioned...they should be singing well past 25psi without too much effort. Thanks for pushing the envelope and sharing your results.

 

As much as I hate to say it ...ask Kyle what these turbos can do...I have always been against the greddy TT kit as it was package as it was not even remotely a bolt on/stock friendly kit. They could have slapped on some 25/30's(a heck of a lot cheaper) and gotten the same gains at 7-8 psi...the people that build will get the true Greddy TT kit. It truly sings above 20 psi....you have a hang up somewhere, it defintely isn't the turbos.


--wes

 

I'm not trying to hi-jack this technical thread by asking a stupid non-technical question but....What it's like to drive this increadible beast???

 

GQ Gq gq... One question you did not address...

To Builder Z

What Is your Altitude above Mean Sea Level.. ?

The thin air... ?

Cheers Amy -

 

HMMMM. the compressor chart does suggest that the tdo5-18g turbos are not running out of air so it could be the problem lies elsewhere.

By my calculations 22 psi should see you @ roughly 675 rwhp (rough calculations probably not very accurate due to altitude))

However there again by the percentages based on what you actually made @ 18 psi vs what you actually made @ 22psi your numbers are spot on.

i put you @ 630 rwhp psi based on your 18 psi numbers as an exact equal percent increase and you actually made 616 so only off by 14 whp which could easily be a margin of error so actually these numbers may not be anything to be concerned about?

But then you go back to your dyno plot and have to wonder whats going on with the hp peak round 5k rpms....???

I just have to wonder about the plenum design when boosting this high. Crawford helps modify this design for more eaqual airflow however the overall factory design itself is still the same and i wonder if this might be the biggest bottleneck in the system(my guess)

I wonder how efficient the greddy plumbing design through the IC is at this boost level.

Have you considered a larger throttle body ??

 

oh BTW here is a compressor chart with engine demand lines i drew up a while back. The chart says there is still room in these turbos and that 22 psi should not be highly unefficient at all. (of course what actually is going on may be very different)

 

first of all iwanted to thank everyone for the compliments and the advice. gq i was mistaken on the timing. i spoke with the other tech helping me tune the z and we did advance the timing(prev. retarded) to almost stock settings. however the ecu was continuing to retard fairly aggressively. so that may be our culprit. according to squill we are not to far off of where it should be. i apologize for the misinformation it was a long night at the dyno and i initially posted before i verified everything with eric. we will return to the dyno once we find a clutch to handle this level of power and torque. os gikken gave up last night at the track. any ideas on a clutch?? z is down until we find one. thanks again jason

 

gq, we spoke with kenji at greddy and he stated that although we can advance timing through e-manage the ecu will not allow it to "actually" accept corrections? we will see once we find a clutch. if this is the case i believe, based on all of your suggestions, that we will rebuild the head. charles i cant wait to see the #'s on your z when it is done.oh and we are still using e-manage with rebic for add. fuel. brian the z is awesome to drive, last night at bandimere(5800 feet elevation) we ran a 12.7 at 118 mph with a badly slipping clutch. thanks again jason

 

Check out the tilton clutches . You are not the first on this board to destroy an os giken clutch quickly. Quite a few high hp supras are running tiltons after destroying other clutches and there are steetable versions from tilton that will hold the hp you are making check em out!

 

squill, thanks for the info. we will take a look. i was also going to look at advanced clutch technologies. does anybody have an opinion on one or both of these clutches? thanks jason

 

ACT will blow up your tranny.

 

lol...gotta hear the explanation on this one.

I've had several ACT heavy duty clutches and I've yet to "blow up a tranny " with one.....care to elaborate.

--wes