Shakedown at track a 13 second disaster- Converter issue?

[Toonin]

Hey guys-
Working on this car for awhile- lots of dyno time and upgrades to get the power level (650whp) we were looking for on 3.8 bottom end.

Important specs are:
3.8 liter
Precision 72mm@ 24-27psi with C16 + Alky
TA 224/224 cam
Champion CNC heads (latest design)
200r4 and mystery converter
Fast XFI + XIM

Now, I may sound stupid- but I had no idea how important the converter was on this small ci large turbo setup- On the chassis dyno it would build a ton of boost and torque at 3000 rpm+ so i thought it would be fine at the track. At the track, we launched it at 8psi, it pulled decently to 6300- shifted, then feels dead from there on out- the rpms barely build to 5500, then it shifts, drops to 5100 then it really feels dead and the rpm kind of stays level hovering between 5000 and 5100 for 4 seconds @ 22psi! How is that even possible? Felt like we were towing a trailer!

I'm going to throw it back on the dyno to see if the motor is still ok- and I notice the cam sync degrees wandering around.

Is this a case of a converter that is just completely wrong for this setup?

For some reason I can't attach a FAST datalog- So I attached a screen shot of it.

 

[bison]

If your converter was built for an engine with boost in the high 20's and you're in the low 20's it's going to be way too tight. The difference between 22psi and 27psi should be over 125hp. You want your converter flashing into the 5500-5600 range at minimum with that combo. Either increase the cylinder pressure or get the converter loosened. There's no converter that can work in both situations.


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[Dusty Bradford]

What fuel are you using? The potential is there but if this is on race fuel, the tune is really holding it back. Without enough power, the converter will not let the motor gain rpm.


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[Toonin]

So you think it's just a lazy tune? I was very conservative with 18.5 degrees of timing and AFR's 10.5-10.8.
I just looked at the dyno #'s again and it was making 641 whp but @ 28psi, and in this log last night I'm down to 20-23 psi max. I did'nt like the boost creep I was getting on the dyno and I ported out the silly little hole on the turbo to match up with the downpipe- obviously that worked- but now I need to re-adjust the boost control settings! I'll get the boost back up where it should be and try again before f-ing around with the converter.

 

[krom]

What is your 0 boost rpm?

 

[Dusty Bradford]

Looking at the graph. It appears to be working for you. The 2-3 shift was early most likely due to the trans just shifting early. It's not gaining rpm because the tune is soft for that boost level. With the extra boost to match that tune it will be an entirely different animal.


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[Toonin]

What is your 0 boost rpm?

You mean at what RPM point does it reach 100kpa/0psi ?

 

[Reggie West]

With race gas you can run 23 degrees of timing and that is conservative. 26 is about the limit on a very good tune and AF ratios dialed in.

If you are running alky on top of the race gas, you should be shooting for an AF ratio of 11 to 1 on the top end. Looking at your screen shot, you are at 10.88 and the ECM is pulling out an additional 10%. Which means your actual AF ratio is somewhere around 9.7 to 1. That means your VE table needs to be trimmed out its still rich. That is the difference between the VE table and the commanded AF ratio table.

I would bet you are running rich everywhere. If you want to keep on using the alky, you need to take out fuel ( reduce the values in the cells).

Remember this: you have to reduce the fuel by 25% when you run alky with gasoline.

Bottom line: I would be looking at the tuning aspect before the converter.

 

[Dusty Bradford]

Reggie. His actual af is displayed in a dark blue so it's hard to see but its matching 10.88 which is the target.


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[kidglok]

I'm no expert on race gas, but id bet its hard to light it off with only 18* timing. I run that with pump gas and Alky alone.


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[Reggie West]

How can that be if the O2 corrections shows -10.2% . I do see what you are saying Dusty but that does not compute.....

 

[kidglok]

How can that be if the O2 corrections shows -10.2% . I do see what you are saying Dusty but that does not compute.....

The xfi is pulling 10% fuel out of the VE table to reach the target a/f of 10.88


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[Reggie West]

Got it.

 

[krom]

You mean at what RPM point does it reach 100kpa/0psi ?

Yes

 

[Toonin]

With race gas you can run 23 degrees of timing and that is conservative. 26 is about the limit on a very good tune and AF ratios dialed in.

If you are running alky on top of the race gas, you should be shooting for an AF ratio of 11 to 1 on the top end. Looking at your screen shot, you are at 10.88 and the ECM is pulling out an additional 10%. Which means your actual AF ratio is somewhere around 9.7 to 1. That means your VE table needs to be trimmed out its still rich. That is the difference between the VE table and the commanded AF ratio table.

I would bet you are running rich everywhere. If you want to keep on using the alky, you need to take out fuel ( reduce the values in the cells).

Remember this: you have to reduce the fuel by 25% when you run alky with gasoline.

Bottom line: I would be looking at the tuning aspect before the converter.

But- Let's say I am running a final mixture (as in what is actually getting into the cylinders) of 75% race gas and 25% methanol- and If I wanted a lambda of .80 (AFR of 11.7:1) with the c16 and lambda of .80 (AFR of 5.12) with the alcohol then I should be targeting an AFR of: (75% * 11.7)+(25% * 5.12) = 10.05. No?

I know I'm real shy on the timing- I've seen on of Cal's tunes that runs 23* on C16, no meth, but this motor is kinda funny cylinder to cylinder and when we ran 19* on Shell 116 + meth it started to melt the tip of one spark plug so I got a bit scared and backed it off across the board.

I appreciate all the input- you guys are really experienced with these motors, and with your help, I hope to take multiple seconds off the time sheets and get down in the 10's without burning up any pistons.

 

[pacecarta]

Remember this: you have to reduce the fuel by 25% when you run alky with gasoline.
.

you would think that but i dont run that way , i run as much fuel as it should take to run my et/mph and the alky is there for the cooling
just target a richer AF
and race gas at low timing wont perform well
with c16 there should be less need for alky as the aircharge temp can be run higher with the additional octane

 

[krom]

But- Let's say I am running a final mixture (as in what is actually getting into the cylinders) of 75% race gas and 25% methanol- and If I wanted a lambda of .80 (AFR of 11.7:1) with the c16 and lambda of .80 (AFR of 5.12) with the alcohol then I should be targeting an AFR of: (75% * 11.7)+(25% * 5.12) = 10.05. No?

I know I'm real shy on the timing- I've seen on of Cal's tunes that runs 23* on C16, no meth, but this motor is kinda funny cylinder to cylinder and when we ran 19* on Shell 116 + meth it started to melt the tip of one spark plug so I got a bit scared and backed it off across the board.

I appreciate all the input- you guys are really experienced with these motors, and with your help, I hope to take multiple seconds off the time sheets and get down in the 10's without burning up any pistons.

Were you using non projected plugs? I have melted plugs when using projected tips when I was to lazy to drive a few miles to get the proper plug.

 

[Dusty Bradford]

When you overfuel a car it places a large load on the ignition system. There's no need for the alky with the C16. In my opinion it's hurting your performance. C16 doesn't like really cold inlet temps that you will get when using the methanol. On C16 I want to see inlet temps no cooler than 80-90 degrees. Q16 likes it in the 50-70 degree range. Your tune is soft for C16, combine that with the methanol and it's overly rich and could be causing issues lighting off the C16. I'd turn off the methanol and focus on the tune.

Also as far as your plug being burned. Too much spark lead isn't the only thing that can burn the tip. Too much fuel puddling in the cylinder can burn valves, pistons, plugs etc....Rich fuel and low timing isn't necessarily safe.

 

[delcowizzid]

Low timing also makes heaat

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