Opinions on turbo/tune

[1fast97gsx]

Well I went out and did a datalog on my car today. Car has ross pistons, eagle rods, metal headgasket, arp studs, 1g head, 1g cams, and an scm61 turbo. I am not really happy with the power it's making just yet. I hit full boost at like 5000 rpm, and I'm running 19-20 psi. Here is my datalog ...

RPM Timing Air Flow O2 bank 1
2704 27 4.82 .12
3052 25 6.55 .90
3440 21 8.39 .92
3848 19 10.31 .92
4316 17 12.93 .94
4860 15 18.17 .94
5492 11 24.51 .92
6112 13 27.02 .92
6700 15 28.47 .92
7148 17 27.41 .92

I thought I would be seeing more airflow at this boost level. I don't have any boost leaks that I know of ... but spool up is VERY slow too. This was a 3rd gear pass. I'm going to richen all the .92s to .94 and do a 4th gear pass tomorrow and see how it looks. At least there aren't any dips in the timing, but as far as the power I should be making with this turbo it's just not there. Maybe more boost, tuning, and some cams?

 

[HighPSI TSi Guy]

cams should help a lot.. but you definitely need some tuning.. that timing curve is really messed up, would be nice to have a more accurate log though.. can you get something better than 500 RPM incriments?

are you sure you don't have any leaks? that turbo should spool much quicker than that

 

[CanadianTSi]

With the negative compensation on the S-AFC it makes your airflow look lower then it really is.

 

[Blk_99gst]

This was a 3rd gear pass. I'm going to richen all the .92s to .94 and do a 4th gear pass tomorrow and see how it looks.

In my opinion, stick with 3rd gear pulls. 4th gear is a lot more load on the engine, so things will need to be a little richer to compensate so you don't know. This will then throw off your 3rd gear numbers, you'll be a little rich in 3rd if you tune for 4th gear. For me, most of my races end at the top of 3rd, so that's what I tune for.

 

[1fast97gsx]

cams should help a lot.. but you definitely need some tuning.. that timing curve is really messed up, would be nice to have a more accurate log though.. can you get something better than 500 RPM incriments?

are you sure you don't have any leaks? that turbo should spool much quicker than that

No leaks that I could find .. I tried a boost leak tester and started pressurizing the system, but over like 12psi the tester would blow off the turbo so I never really got it pressurized at 20psi or anything that high. It's wierd though too ... I have an external wastegate set at 1.0 bar standard. I went out to program my boost controller ( hks evc4 ) and I did the 2 learned mode passes and it came up with .89 bar for my stock boost. A week ago or so I set it up and it was .99 bar .... is this another indication of a leak?

Another thing I just thought of was to install the turbo I had to install a 1/2" spacer plate between the head and the exhaust manifold. I just used longer studs from ace hardware ... maybe the studs are stretching or the spacer plate is for some reason not perfectly level so I'm loosing exhaust before it even spools the turbo? This still doens't explain the .89 bar boost the controller is recognizing instead of 1.0 bar it once recognized before ... the guage does read just a tad under 15 just like it should though. Too many problems!!!!

 

[1fast97gsx]

cams should help a lot.. but you definitely need some tuning.. that timing curve is really messed up, would be nice to have a more accurate log though.. can you get something better than 500 RPM incriments?

are you sure you don't have any leaks? that turbo should spool much quicker than that

I'm gonna check out the palm and see if I can change the incriments. What do you mean the timing curve is really messed up? Too high before it hits boost?

 

[Blk_99gst]

I'm gonna check out the palm and see if I can change the incriments. What do you mean the timing curve is really messed up? Too high before it hits boost?

You change the increments on the palm by getting the best sampling rate possible through the byte timing setup menu. I'm getting about 17 samples per second on my 99gst.

Your timing curve really isn't that messed up like 1fast97gsx said. It looks messed up compared to the typical log file, but typically we see people who hit boost say at 3000 or 3500; at that point is which timing should drop because of the initial huge airflow, and then timing starts to climb from 4000-7000 as the ecu awards more of it. But in your case, if you're not getting boost until 5000 rpm, then that is when your initial timing hit occurs, and then climbs after that. But to most people it looks like you're knocking at 5000rpm because your timing gets pulled compared to 3000 or 3500 rpm.

Either way, boost at 5000rpm is WAY slow. To spool up that slow, you would be able to hear the exhaust leak between the mainfold and the turbo. A few months ago I had a pretty audiable exhaust leak at it was because my mainfold to turbo gasket had partly worn away. It affected my spool just a little bit, but not too much.

 

[1fast97gsx]

Yea as far as the timing curve I thought it was ok but of course I'd need more incriments to know for sure.

As far as the late spool ... this is only at 20 psi. The turbo is an scm61. I've been reading on the forums that I should be seeing full boost around 4500 already with that turbo, and 25+ psi by 5k. I did a compression test on the motor and it's all around 165-170. I'm going to put a stock headgasket back on instead of the 4 layered metal one I'm using now .. hopefully it will bump compression up a tad and give me some faster spool and hopefully some more power. Realistically though, if there's no boost leak .. and compression on the motor comes out good ... what could be wrong?!!? The motor only has 900 miles on it, and the turbo as well. It couldn't be a worn / broken turbo so soon???

 

[CanadianTSi]

You could have an exhaust leak pre-turbo...

 

[1fast97gsx]

yea that was my only explanation. Checked for boost leaks and found none, however I had to use a 1/2" spacer plate to keep the turbo from hitting the water pipe and I had to get longer studs ... I'm thinking the spacer plate isn't perfectly level or something.