Rb30/26 Final Tune Feedback

[leeroy_25]

Okay guy's so I went back to the dyno at the weekend. Had no time to get a new wastegate spring. So I tried to put some pre-load on it. I had made a new MAF table for the Q45's and raised the airtemp correction value and also increase the warm water correction temp as the car never seems to get over 70deg and this seemed to solve the random problem of the car getting richer every run! My tuner then trimmed up the fuel some more (still running very safe) and did a few runs but still the boost was dropping off as the revs increased. In the end in a effort to try and get a representative run my tuner held half throttle to build the rpm up to around 5000rpm and then hit the throttle to try and get the boost to hold out for redline. Still no joy! Anyway. In the end I came away with 451bhp at the rear wheels. with the boost dropping off below 1.1bar! So would estimate at least another 10-15bhp if I could hold boost on the dyno. Annoying because it holds boost on the road fine!

Another graph and video below! I am pleased enough to call it a day now unless I have good reason to go back later! Essentially I am just chasing proof of a big number on the dyno!

The whacky graph is from where we tried slamming the throttle at the end of the run!

A quick little video clip too.. Not that great. But hey!

Edited July 25, 2011 by leeroy_25

[Top end drag]

Seems like you have a bit of a flow issue

Bigger, thicker intercooler and exhaust will open it up and get you more power.

The difference in my car with just a proper front mount was incredible. Open up that exhaust, 3" or bigger and remove the cat.

How is your fuel pressure under boost? I had an issue, my fuel pressure dropped 10-15 psi from full boost as I climbed the rpm's. Resided the pump to the battery and it solved the problem. Also scrapped the 60mm eBay wastefate for a turbosmart 60mm and that made the world of difference. I run a holder hx40, stock rb25 and bolt ons and made 492 at the rear wheels at 19.5 psi. Your set up with a few changes (fmic, exhaust, fpr) is all you need in my opinion. My first tune was 474 rwhp and with the fuel pump wired to the battery and new wastegate it did 492 rwhp and boost came on 300 rpm quicker.

[leeroy_25]

Hi There,

Only just seen this reply!

Tanks for the feedback.. I would agree with you I have some kind of flow issue! Strange how it holds boost fine on the road but not on the dyno is the weird thing? I can only assume it is the lack of airflow in the dyno cell?

I am running a stock intercooler and may well look for a larger one in due course. For now I redid the exhaust and put a stiffer wastegate spring in and went back for another run. Gained 1 bhp top end! But was still getting the same boost drop and also wheel spin problems. I did make quite a big gain in the low down power and torque though which was nice 30ftlbs of torque and I think similar in the power. My cams are set to maximise low down power and torque and not top end so I guess it depends how you set yours as to the power difference? in our setup? You also mentioned fuelling.. As I am I don't think I can support much more power as the duty hits 90's top end.. not sure if that is pump not keep up or the 600cc injectors are too small? I don't have a FPR/gauge inline to check at present.

You say you are running an old HX40?? As in an H1E? What size turbine housing is it? What rpm do you hit full boost out of interest and what are you rev limited to? interested to know someone else experiences with a holset!

I ended up setting my boost to 1.3bar.. (18.8psi). I didn't fancy going any higher especially as I cannot hold that on the dyno to map the top end properly!

[XKLABA]

when you say it holds boost on the street, are you running 4th gear to the rev limit same as the dyno? or is it in a lower gear, cause in a lower gear the engine isn't loaded up as much so it isn't sucking the same air.

which stock intercooler do you have, because all 3 GTR intercoolers are different with the 32 one being best for flow but not for cooling,if it is a 33 intercooler ( which i have one here ) I would start there next and make sure it isn't the issue, cause if it is a resriction then it could be lifting the intake pressure to the intercooler higher to get the pressure at where the reading for EBC coming from to 18psi which would increase intake temp aswell as add back pressure to the exhaust manifold.

I have seen these intercoolers make close to this power on a 2.6 but the 3ltr might use more air, also what comp ratio do you have