Here are my dyno results from last Friday. The
three runs here are ALL on the exact same settings but with varying results.

My "5th run" was my best 356.
My 2nd, 3rd, and 4th were in the 340's

All runs after like the 6th went terrible. Even after I changed my maps back the last 4 all went lean.

Intake Temps on the PowerFC stayed between 38-43 C plus or minus 2 degrees. Water temp 82-85.

Any ideas on what happened?

Here's the best one first

 

2nd one (actually before the other) 340ish.

 

best one...356

 

one of the last ones...like 300 , a loss of 50 hp. All the last ones were like this and going lean.

 

mods

 

Could there have been an issue with the fuel pressure?

 

Possibly, I wasn't looking at my fp gauge and I can't log it (at least yet...). Since then those boxes have seem a little leaner (N16-n18 : p18) than they use to be. They use to be rich and I leaned them out before.

I'm going to inspect the plugs too. They were in perfect shape the week before so I will have a definite before and after comparison.

 

I hope you are using a Fuel presure regulator that sends the fuel pressure up 1:1 and not 2:1 or 3:1 etc...
I Think RRFPR means rising rate more that 1:1 (depends on what book you read).

 

Weldon 2040. I'm not really sure to be honest. I thought it was a Rising Rate, and I though it was the Raising Rate that goes up exponentially.

My fuel pressure is about 2.25-2.50 kg/cm2 unless under acceleration which seems to put it at 4.5. There are very few times it's anything in between.

I've always been confused by this behavious but previous posting to this forum and others have never yielded any results. I thought it was supposed to start out at say 38psi and then add 1 psi for every pound of boost. Mine doesn't seem to really behave like that.

 

Were you on race fuel of WI? I'd do a comp check with air/fuel like that.

 

The WELDON 2040.200.#### are 1:1 units for fuel injected setups. I hear that this unit does a pretty good job of keeping the differential pressure across the injectors constant for a wide range of flow rates. It can handle some big pumps.
The rate at which you boost climbs should be the same rate at which the fuel pressure climbs. This would be easy to see if you were looking at same unit of measurement for each system.

 

No, 93 octane as always. My compression sucks and has sucked since the rebuild. It's okay on the rear rotor but the front rotor is uneven and low.

The only part the a/f worried me are those three boxes at basically full boost (set at 1 kg/cm2) at basically 6000-7000 rpm. It was fine for the first runs, all I changed thereafter was timing split to see if it made a difference and some lower rpm/boost fuel take outs to smooth out my rich dips. I just don't know why that area abruptly changed resulting in runs that were 50hp less than the initial ones.

Honestly, I'm happy I broke 350. Knowing the compression has sucked I had a feeling I was going to be disappointingly low. I just wish I had kept a consistent 340-350 all the way through or at least knew what happened.

 

is the rpm right on that last dyno sheet? you're revving it past 10 grand?

 

No, I forgot to mention that. They couldn't get the rpm picked up and no accurate torque values eit.her.

I'm going to take to another dyno in Tampa that was recommended soon.

I cut it at 7100-7200 rpm on all runs.

 

Where were they placing the wideband? It was before the cat?

James

 

They put it in the exhaust. It was pretty close to my FJO and I was datalogging the runs. They agreed usually from what I could tell visually.

 

Thats cool.....do you have cats?

James

 

HF Cat from pettit.