hi to everyone i need your insight here
we had a gsr with b16 head je pistons 10.5 comp eagle rods itr cams
topmount mani edelbrock victor x mani the turbo mani
precision 6162 with 63 ar,76 mm downpipe just has a 63 restriction just after the turbo,and 76mm exhaust,big i/c
we had a problem with the car spining on dyno it was in maha dyno
also the graph says the torque and hp falls at 6300 but the dyno says that hp falls at 7500,can this be from spining? also the car was at 1,2 bar almost 19 degrees of timing using neptune that is a great software ,we reduced timing the power falls we increased timing again the power falls at the same spot,whatever we did we had the same situation,vtec engaging at 4800
i would like to know your in
put for this,it was a dyno spining? it was the turbo gone bad,what could cause this situation,tuned on 95 oct fuel
here is the graph
thanks for reading

 

its just the way the turbo behaves. A big mid-framed turbo will cause the tyres to spin if not strapped down properly or using crappy tires on the dyno. you have to put some weight on it, and keep tuning. Its a peaky turbocharger. The .63A/R isn't much of a restriction with mid-range power under 650whp with that wheel.

 

thanks for the reply soadan i have read many informative posts from you before i got registered, i searched a bit on this issue it seems some people had the same issue as we did and is like hitting a wall ,my concern is that the donwpipe follows the housing of the turbine exhaust housing at 2,5 inches for 10 cm and then getting bigger to 3 inch,
we made many cars with similar turbos and none had these problems,we did put weight on car we also putted a bar plate on the engine and this helped a lot,
the last think i could imagine is that the car had a problem with the ignition coil they changed it with a used one and the spark plugs was ngk but iridium,could this cause a situation like this? i will try to make a photo of the downpipe for you to see
thanks again

 

here is the photo of the downpipe

 

That's actually fine. Part of an exhaust vortex effect. (The GT 3" V-band series does that as well on the turbine housing.) So that's not your issue. you're using a BIG turbo on a Top mount manifold, at that power. Its the way its going to behave. Peaky...

 

Just the nature of the beast, if you put that 6162 on a manifold with smaller runners you'd be amazed at how the behavior of the car will change.

Look at gringoteg's thread, he has of the first original 6262s on an ETS forward facing, short runner manifold and his turbo has amazing response, almost gt30r like for the turbo size.

 

thanks again both of you for helping me,i apreciate your answers very much,we were about to change the downpipe so we will not change it,what is your suggestion to make the car hold power to the top,we can change the exhaust housing to an 84 a,r or take a new bigger turbo,or change the manifold to a ramhorn style? the car was about to beeing tuned on c16 we were excited how much timing wanted in 95 oct considerintg is a 10.5-10.7 cr engine but having this problem made as let it as it is without tryying to tune it on c16

 

also forgot to mention the car made 376 hp not so much to my point of view at 6500
and 39nm that translates 28.7 lbs/ft

 

Bump good advice

 

This really looks to be more of tuning issue or wastegate issue more than anything else, but your information is limited.. More specifically, just based upon experience with that turbocharger, it could be in the ignition timing that's being used with engine management you're using. (And no, its not exactly a set number that it should be at... you need to speak to another tuner of good repute to get some guidelines). Or, on the mechanical end, the wastegate spring may be too small in which boost may not be holding steady with the boost controller you're using.. Again, hard to say.


Scenario A - Ignition?
It could also be that the stock ignition that you're using may be "tired" and simply can't hold spark in the upper rpm band. (Be it from the possibility that it is an old unit, bad ICM, or bad ignitor) to which you may need to swap out to new units, or at least enhance the ones there with an external coil, a new Accel internal coil, or perhaps even a separate ignition.

Yes, the stock ignition should be able to hold fine, but no one here can get into more detail without sending a file to someone in the Engine Management section (depending upon what management you're using). You'd know something is up if you're breaking up in the higher rpm range.

Scenario B - wastegate?

You never mentioned what wastegate you're using, boost control type or spring being used to control that wastegate. Even something as simple as a boost leak could cause issues in the upper rpm band, to where you're just not getting as much boost pressure through the system as you think. It may be time to do a boost leak test, or check the configurations of your boost control (both electronic [settings] and physical connections [i.e weak collapsing lines, tears, holes, etc]). VTEC being set low has little to do with the problem unless you're back to the timing issue.

This could be from a few things. time to get a couple of second opinions from some tuners with your files, and make a mechanical checklist to make sure things are ok. But without a lot of information for the people that have the ability and skill to diagnose with tuning ignition and fuel trim maps, more information is needed. This is where you may want to talk to them for better direction.

I'm sure you'll figure it out.. good luck.

 

the wastegate is a tial 44 mm with 15 psi spring, i tune the car,i have tuned many similar setups,never had a situation like this, i will not tell that my tune is the best,i dont like arogant people even they have great knowlegde, i just tuned the car with the same way i tune everytime, it picked up some hp adding some degrees and then stop gaining power,then whatever i did in this certain area nothing good came up and the problem was getting worser or similar,
i hope this could get you in the situation and also apreciate your help in the problem

 

No problem. Time to check for leaks, and have a second pair of eyes for your tune.

Also, how are the valvesprings / retainers in this thing? Old? replaced? recent?
I've also experienced how some older / worn valvetrain contributes to the loss of power on the top end due to valve float from the springs just not being able to recoil well. It doesn't exhibit exactly the amount of loss in the upper-rpm band that I'm seeing, but it could be a factor to other things.. Just an idea.

 

i didnt mention the valvetrain because it has full ferrea valves retainers and springs its a b16a head, i will make you a screen shot of the high ignition map,i talked with the buider to make a comp test everything was good as he said to me,we checked about leaks in the i/c and piping nothing everything was on spot,
i also want to make a second try on this before they buy another turbo because for me is useless if we dont find why the car acted like this,this motor has 10000 km till now and running strong

 

I'm talking about vacuum leaks on vacuum hoses, intake manifold, clamps.. The Intercooler piping is just on the surface. Good that the valvetrain is new, hopefully installed properly... You can't assume much when we know NOTHING about this setup other than what's typed and a map shown.. Be thorough.


And for goodness sake, Don't send that map here. GO TO THE ENGINE MANAGEMENT FORUM and discuss the situation with others, while linking this thread. Kill two birds with a stone.

 

also forgot to mention the tb is 64 mm ,dont worry i will not post the map here,i understand you,thanks again