Roe SC tuning questions

[KenH]

As some of you know, I have been tuning my Roe system myself using a WBO and open road (along with some help from Sean Roe). Mods are in my signature, but basically a 6.5lb system with water/methanol injection. Car is basically running good on the street with a litte detonation noticable intermittently when getting into the throttle. I know that others such as JD have reported the same thing. I finally had a chance to put it on the dyno and here are the results. Dyno is a Mustang dyno.

HP is about what I was expecting at 571. I was hoping for 575 and I did shut down a little early and it was still climbing. The torque however seems on the low side at 566 and I was expecting something closer to 600.

Here is the graph from the VEC2 logging showing the A/F as logged by my built in WBO as well as the water injection, timing advance and boost. The A/F is running pretty flat around 11.25 on average and staying between high 10s and 11.5. On the open road testing it seemed to run more in the 11.25 to 11.75 range.

There is a lot of boost creep that goes away in the middle of the run right around where I advance my timing. Some people thought that they heard a little detonation somewhere in the middle of the run as well, but I did not hear it. I have tried to keep my A/F and timing on the conservative side since I am still running the cast pistons. I have 3 degrees advance dialed in at max with 92 octane gas.

Anyone see anything here that would explain my low torque reading or otherwise looks too far out of whack?

Any ideas about the inconsistent boost creep? 10psi seems like a lot on a 6.5lb system. I have also heard of 5lb systems seeing up to 10lbs as well. Is everyone else seeing similar boost creep?

What about the timing? Is everyone running a similar kind of retard/advance curve or has anyone come up with something better?

 

[Schulmann]

Hi Ken !

Nice run.
I have also a similar setup to yours.
My Viper makes 601rwhp with 600torque on 94 oct fuel.
However I spent a LOT of time tuning it.
Check my photos in my archive. I have a couple of prints of this run.

A question, what fuel did you use ?


8-10psi is normal.
However that sudden boost drop between 4000rpm and 5000rpm is curious.
I am not sure what it is.

Timing seems to be good, agressive in the upper RPMs.
You could try to zero the ignition retard below 4000rpm.
So you could gain some torque.
But be very care full when you test it ! Listen to possible detonation (sanding...).
Do the test on the road, on the dyno you would just hear a big boom ...
If you have detonations with zero retard in lower rpms then be carefull also in the upper rpms.


Water: depending on what fuel you have maybe you are injecting too much water.
Again test on the road. On dyno, all errors are fatal.


AFR:
I prefer to run between 11.8 and 12.3 (this is agressive too).
I try to set my AFR to 12-12.2 sharp.
Going from 11.2 AFR to 12.2 provides often 5-8% gain in power.

Be carefull when testing.

A.

 

[Joseph Dell]

What % **** are you running? the more ****, the more timing. if 50/50, then you are running a really conservative timing which would explain some of the power drop. But to Schulmann's point, it could be too much timing. finally, you are a little rich which would explain the power flux. with water/****, you want to tune closer to a 12.0:1 target. with jsut the SC, closer to 11.5:1. But what kind of fuel do you get out there? OR? isn't that 91 only? that could make a difference...

JD

 

[KenH]

Thanks for the response guys. I'm running 92 octane and 50/50 mix on the injection.

I agree that I need to bring my A/F up a bit. I was running in the 11.8-12.0 range when I was running windshield washer fluid, but the 50/50 mix I am running now has richened it up a bit. I actually leaned it out a bit before the dyno run, but apparently not enough. I'll dial it up to 12.0.

I might also try reducing the amount of timing retard in the lower end and see how it responds. Before I started running the 50/50 mix, I couldn't run much more than 3 degrees advance midrange without getting detonation. I might try bringing that up a little as well and see how it responds now.

As for the amount of water/methanol, I did have a problem with drowning my motor when the injection first came on and I got that fixed. As far has how much I am injecting mid and upper range, I haven't tried to do much fine tuning with that. The water/methanol injection side of the tuning is still a bit of a mystery to me.

 

[MaxedGTS]

Thanks for the response guys. I'm running 92 octane and 50/50 mix on the injection.

I agree that I need to bring my A/F up a bit. I was running in the 11.8-12.0 range when I was running windshield washer fluid, but the 50/50 mix I am running now has richened it up a bit. I actually leaned it out a bit before the dyno run, but apparently not enough. I'll dial it up to 12.0.

I might also try reducing the amount of timing retard in the lower end and see how it responds. Before I started running the 50/50 mix, I couldn't run much more than 3 degrees advance midrange without getting detonation. I might try bringing that up a little as well and see how it responds now.

As for the amount of water/methanol, I did have a problem with drowning my motor when the injection first came on and I got that fixed. As far has how much I am injecting mid and upper range, I haven't tried to do much fine tuning with that. The water/methanol injection side of the tuning is still a bit of a mystery to me.

how do you tell how much detonation your getting and when??? Max

 

[Schulmann]

Detonation sounds like sand hitting the fenders.

I don't think that on our level the W/M mixture % has a large influence on the torque. Rather the quantity of fluid injected is more important. With a 91 oct fuel under even 1 psi boost I inject nearly 100% W/M. My mixture is rather 20% methanol and 80% water. When racing I use more methanol.

Ken, on 92 oct fuel you should be carefull with the ignition.

 

[davem]

I have some friendly advice for you:

A "little" detonation is not acceptable. Stop tuning for power and get rid of the detonation first, then start tuning. You must eliminate this completely or you will be doing a rebuild in short order. Pull timing and add a little fuel - you need to pull the timing 5-600 rpm before you hear the detonation, it's much easier to prevent detonation than to eliminate it once it starts.

I'd say it probably is detonating at 4000 or so as your friends have mentioned, you have quite a boost dip that follows your ignition advance. I have not seen that dip on any other car.

good luck,
Dave.