Small 16G to 20G and the car is not any faster. What am I missing?

[Grizzly Racing]

I was running a small 16g that was consitantly turning 12.40's @110-112mph. I was running the small 16G at 24psi.

I just upgraded to a 20G and set the boost to 25psi and went to the track. The car is running 12.40's at a max of 110mph.

I upgraded injector size, but everything else remained the same between the two turbo's. DSMchip Eprom was used for the tune.

I was able to get a log off the 20g and was getting zero knock, timing pulling to 17* at 7000 rpms. This is what I was getting on the 16g as well.

All supporting mods are in place. Car is a 91 gsx.


What I am doing wrong here? Why is the car no faster then it was before?

 

[GDNF2ET]

If your getting 0 knock, you need to turn it up till it knocks, then turn it back and tune some more..The 20g is more efficient at more boost then the 16g..Contact your chip guy and tell him what you need with this setup..You had the 16g screaming, the 20g is just getting started..Maybe your intercooler is holding you back now ?

 

[JusMX141]

This isn't uncommon. My buddy's 2G went from running a 12.55 @ 109 with stock cams and a TD05H 20G to a 12.35 @ 113 with BC0101 cams and a Frank 5 20G (60-trim Garrett compressor, TD06H turbine) at the same boost level.

The car does have a completely different powerband, however. I think it's way more fun to drive the way it is now than it was with the 05H 20G.

The problem is that at 20-22psi he's barely touching the efficiency of the 60-trim / TD06H combo. This turbo allows MUCH more potential than the 05H 20G when he does decide to crank up the boost.

 

[pboglio]

Airflow values would help, as well as a "full" mods list. You changed the injectors which means A/F ratio has now become a variable. A log file would really help out.

Also, was your fuel type (i.e. racing gas vs. pump gas etc.) the same between the 16g and 20g runs? Outside ambient temps between both runs? What did the boost curve look like on the 20g, did it hold a solid 25 psi through out the rpm band?

I'd really like to see how much airflow your running, it should be around 40-42 lb/min at peak power on 25 psi. If your flowing that much but your power is down then your problem is tuning for sure (i.e. A/F ratio or ignition timing). If its NOT that much then I'd suspect your either not holding 25 psi at peak power or you have a restriction somewhere which is limiting power output.

I'm assuming your running some kinda cam upgrade, big honking FMIC, testpipe, 3" catback, etc.

More info needed

 

[Black_Bullet]

Airflow values would help, as well as a "full" mods list. You changed the injectors which means A/F ratio has now become a variable. A log file would really help out.

Also, was your fuel type (i.e. racing gas vs. pump gas etc.) the same between the 16g and 20g runs? Outside ambient temps between both runs? What did the boost curve look like on the 20g, did it hold a solid 25 psi through out the rpm band?

I'd really like to see how much airflow your running, it should be around 40-42 lb/min at peak power on 25 psi. If your flowing that much but your power is down then your problem is tuning for sure (i.e. A/F ratio or ignition timing). If its NOT that much then I'd suspect your either not holding 25 psi at peak power or you have a restriction somewhere which is limiting power output.

I'm assuming your running some kinda cam upgrade, big honking FMIC, testpipe, 3" catback, etc.

More info needed

+1

The chain is only as strong as its weakest link.
Therefore slapping a bigger turbo on will not increase airflow IF you have something restricting air flow beyond the point your at now. Putting a bigger turbo may have just altered the power band by slowing spool and robbing midrange torque...

Also, a tdo5H 20g isnt too much better than a Evo3 16g.
The tdo6H 20g would likely offer noticeably more power.

Were your times between both runs on pump gas or race gas.
Your traps/ ET arent bad for a 16g, but I can tell you right now you still had a LOT
left in the 16g setup, even for just pump gas. Do you have cams? Most people should start ecking more out of their old setup first before jumping to a larger turbo. If you push your old setup to a higher level, the gains will be much better when you do upgrade the snail IMO.

Also, to go over the basics, do a boost leak and compression test and verify the motor is running decently before blaming the turbo. Whats the AFR and how does your ign timing look across the power band.... You possibly can get another 2 degs of timing out of your entire power band. For 1g compression pistons, 17degs peak is a bit conservative; depending how the rest of the curve looks. BTW; I run 19deg peak timing on my E316g on a 25psi tune with a crappy ebay fmic and 93 octane FWIW.

Post back your findings.

 

[Grizzly Racing]

Outside temp of 82 degrees, the same temp between both 16g and 20g. All runs are on 93 octane pump gas.

20G@25psi. Held 25psi solid all the way to 7500rpm.

Here is a list of mods:
FMIC 20x10x2.75 RRE griffin core. 2.5" piping.
walbro 255lph
AFPR
750CC FIC injectors
MAF-T 3" / Eprom chip
95 pistons
ported 2G head
3" turbo back exhaust, no cat
webcams 546/547 grind

I did compression check today. Same across all 4 cylinders. 165psi. I have not done a boost leak check.

I do not have a wideband. Only boost gauge and EGT.

Here is a log of last nights run.

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[pboglio]

Well, it doesn't look like slow spool, since your airflow is shooting straight back up between gear shifts.

I can't decipher airflow in hz, but 1607 HZ looks extremely low, I'd expect that out of a 16g car on low/moderate boost. Given you have a MAFT I wouldn't trust the airflow reading.

25 psi to 7500 rpm, hmmm. I'm looking at a log of a very quick 20g, trapping 121 mph. All I can say he is NOT holding 25 psi to 7500 rpm. Maybe 23 psi at 7000 rpm, and 20 psi at 7500 rpm. This says to me you have a restriction somewhere or something on your setup is limiting power, which would allow you to hold boost to redline. That kind of boost at 7500 rpm would give you almost 48 lb/min and you would be trapping a crap load faster than 110 mph if that where the case, more like +120mph.

Only time I could hold megaboost to redline was when I was running stock cams. As soon as I upgraded to HKS 264/264 my power went up about 25-30 h.p. but my boost dropped off bigtime. There is something about those Webcams I don't trust, the fact you can hold so much boost to redline makes me think twice about them.

The WEB cams have not been known for being reliable or for making great power.

 

[CanadianTSi]

You could have a boost leak or the new tune may be off (rich)

I would suggest investing in a wideband.

 

[Black_Bullet]

pboglio, you may definitly be onto something about his boost holding that long.
There definitly has to be a restriction in this setup.

OP, what size is your intake pipe, your intercooler pipes, Dp, what exhaust mani and o2 housing do you run. Im just trying to come up with anything that could lead to a restriction of flow, 25psi to 7500rpm on a cammed motor sounds like 30r terroritory.

Hell my car did 109 traps on the e316g on 19psi with a basic pump gas tune and stock cams.
For 25psi and a 20g on a decently set up car, a 110-112 mph trap speed is slow even with stock cams, and its not like the web cams have subtracted h. power even if they arent the best cams.

Yea and I agree on the wideband, your AFR could be way rich. Do some pulls and go check your plugs.
Does the car misfire or anything?

 

[Grizzly Racing]

I took the car out last night to get a better look at the gauges and logger. First I turned up the boost because I have been getting no knock. The boost spikes to 30psi and fades to 25psi by redline. It does not drop below 25psi. Still no knock.

I was also able to check the EGT gauge. Its only hitting about 1450*F at 7000rpm. Rich?

The airflow hz reading on the logger shows 3100-3300 at wot, I don't know why it shows 1607 on the viewer.

Intake pipe is 4" with a large KN filter, located in the fender/wheel well.

O2 housing is a 2.5" dump housing

The car pulls very smooth with no misfires.

I will test for boost leaks and see what I come up with on that end.

I definately think I need to invest in the wideband to figure out exactly what is going on.

 

[Black_Bullet]

Maybe your clutch is slipping the whole time