Need help, having some unexplained issues after an engine upgrade.

[Kinnu]

Hello,

I hope this is the right place to post this kind of thing. I am from Estonia and I apologize for any bad english you may find here.

We have a nissan s14 driftcar with a 2005 GTO LS2 engine. This year we decided to upgrade it with a cam and intake. We bought texas-speed cam 228R 228/228 .588"/.588", FAST 102 intake, new springs, pushrods etc.
cam link: http://texas-speed.com/p-1148-texas-...-camshaft.aspx

Other upgrades: Sikky headers to a double 3" exhaust.

Since we don't have here anybody who knows HP tuners well enough to tune the engine, we got the tune from Texas-Speed. But on the track the engine sputtered in the lower revs and it felt like there was not enough power. Then we went to the dyno and the results showed that the engine had stock power. 265HP and 450Nm/tq from the wheels. We got the same result a year back with stock parts. And there was heavy sputtering starting from 1500 rpm. Then we made some fixes, changed o2 sensors, spark plugs and fit a washers under rockers to be sure that the valves are closing perfectly. After these changes the heavy sputtering was gone and the engine seemed to be working better now. For just in case we measured compression while hot and cold, all cylinders were near 15bar.

Now we went back to the dyno and again got the same results. Then we started to measure mixture and in the lower revs it was very lean, in mid range it was perfect and starting from about 4500 rpm it got very very rich. Then we made corresponding changes to the MAF calibration table and it started to get better, but then we had KR kicking in hard. After that we focused the spark table and tuned it to be at our needs for the KR to be at zero. All this work and all we got was acceptable mixture, but no power. Then I got an idea to compare all the tables and the discovery was shocking.

First I compared original and texas-speed tune maf tables and they had added everything in a logical way, but when i compared our mock up to either of those tunes then there is a drastic drop in the higher revs and by numbers in the log it was nearly a 100 less in the reading. And even more weird is that the spark table correction we made matched 100% to the original tune's spark table. So in few words, we have a bigger cam, better intake and we have to run less fuel and OEM spark table to have the mixture right.

Below are some files:
original tune.hpt - The tune we had when we got the engine, it was supposed to be OEM
texas speed tune.hpt - The name says what it is
first.hpl - First dyno pull log with Texas-Speed tune
Final tune.hpt - Final tune by us
last pull.hpl - Last pull log with final tune

Things I have tested up to this point:

Timed the cam and found out that it is timed. There was a 2 degree difference from the crank to retard, but this should not loose us that much power.
Swapped ignition coils - nothing
Measured Cylinder pressure as described above - all in 15 bar range
Removed the top lid of the intake and saw that it is not perfectly aligned to the heads, there is a 1-2 mm ledge and the injector holes are also not perfectly in the tip of the cathedral port, but again I doubt that it causes such drastic problems.

I am quite sure that it is some mechanical issue, but you guys here have seen quite a lot of logs and tunes and maybe have an answer to this, because guys at Texas-Speed are also clueless about it.

Thank you in advance!

[ingsteve]

remove all torque management and ETC to 100% and try again.

[Kinnu]

Worth a try, but is there any reasoning behind that? Because I'm wondering how can the PCM register the torque? It is manual trans and there are no sensors attached to the trans, as far as PCM is concerned the gearbox is always on neutral position.

[willz28]

Dont know how much it might help, but your log only shows your throttle at 88% during the dyno pull.

[Kinnu]

I am going to have to rule out the throttle position. Did some research and it has to be on 88% if you log TPS, if you log ECT then it shows 100%. Explained here: http://www.hptuners.com/forum/showth...s-ETC-Position

[naf]

wheres your trim, your MAF is all wrong...

Plz activate your Trim and adjust your MAF. Later install a WB and tune for 12.2-5 AFR at WOT from 3,500-Redline. Your fluttering will reduce and your

[Kinnu]

I know that my maf is all wrong, thats why I am posting this here, but it is the only AFR stays in the right range. We had even 2 WB's installed and made the corrections to the maf table corresponding them. We shut of the trim for the pulls, to get the exact reading from the table and not let ecu to interfere.
There is not a big chance that the core of this problem is tune related, I posted this here, because you guys have great experience and maybe have seen that kind of problem before. It is something mechanical or there is some electrical what is not working as it should.

What would cause a situation where there is too much air going in the engine at lower revs and not enough in higher revs. MAF is dead?

[naf]

Intake manifold leak would do that...Or a hole in one of your hoses from the intake tube to engine or from engine to intake manifold...

If you have a readout from the MAF its working.

Your compression is 15:1?

[Kinnu]

No cylinder pressure is 15bar. CR is stock 10:7:1 if im not mistaken. When we get the thing back together, then i'm going to swap the original intake back on. Maybe FAST is leaking and causing those problems, because we only have the hose from valley cover to intake connected. All others are blind.