Well, finally got the car on the dyno today. The Moates Ostrich was awesome! Slorvette was able to make changes on the fly without ever having to turn the car off.

The bad news is that we found out my fuel pump is dying. The pump was only able to sustain ~28psi once the engine got to ~4200 RPM. Putting a new fuel filter in didn't help the issue either. This kept the car lean around 14.6:1 no matter what Slo' tried. No matter what was tried, more fuel couldn't be dumped in. The injector pulsewidths were max'd out and the adjustable regulator wasn't maknig much difference. So, once we verified the pressure was down we called it quits for the day.

Besides that issue Slorvette was still able to gain 8 peak HP, 7 peak Ft.-Lbs, 4.5 average HP, and 4.5 average Ft-Lbs with only 5 pulls.

HP (Before/After)
5000 RPM: 245 @ 14.4 AFR to 253 @ 13.7 AFR

Torque (Before/After)
4100 RPM: 286 @ 13.8 AFT to 293 @ 12.7 AFR

This was all done on a Mustang Dyno 1750. It is a bit of a shock when you are used to a Dynojet as the #s are WAY lower to what you are used to. My numbers on a Dynojet last time were 322 HP and 369 Ft-Lbs., but I have no clue what shape the pump was in then.

Cranking the AFPR over fattened the bottom when we were trying to squeeze some extra fuel out for the top end on the last run.

 

Your fuel pump is killing you...

 

Yep. The plan is to pick up a Racetronix kit in the next week or two and go back.

 

Dyno's are fun aren't they?

Now heres the next shocker..

Your going to put a fuel pump in the car and go from 13.7 to 13.2 and actually loose hp if your not careful.. If you don't loose any you will not change more than a couple HP..

Lean cars always produce great hp, they can slack torque sometimes but that doesn't start happening until past 13.5 or so.

This is why you see alot of race cars and even nascar guys shoot for really lean AFR's.. I personally saw 4 engines on engine dynos at a local big shot nascar engine shop and the richest cylinder was 13.7 and the leanest was 14.4

 

Hi Alvin.

I don't expect to see a huge jump with the pump, but I definitely want it in a "safer" range than where it is. Once we can get the A/F flattened out and can play with some timing we'll see where it goes.

 

I'm expecting a little more than 5 hp gain. Based on his previous track times and the results I've seen from this dyno, I'm thinking closer to 20 hp.

I've heard of similar results of what Alvin's talking about. Haven't personally seen it though. Definitely haven't seen it in your typical street car type stuff.

The Ostrich is a real neat deal. I give it a big thumbs up.

 

I'd be pleased with that. I still at least happy we found a problem, thats progress alone to me.

 

I put everything into excel, cleaned things up, made the charts, found a math error of mine.

 

I dunno, when I had my one lean chip, 13.8-1, it sounded like someone was trying to neuter my car. It REALLY sounded like it was struggling to make RPMs.

 

It might have picked up knock retard. All things being equal a lean car will make good power.

You just have to deal with the safety of it.. Theres a tuner here locally that tunes all his cars to 13.5 and higher.. that is why they don't run good at the track and why I have to re-do stuff that hes melted down on his dyno.

 

Scorp,

Happy to see you like the 'O'. Makes tuning 100x easier and faster huh!

 

Hello Alvin!


In my personal experiences and studies on other peoples work most engines do not tend to live very long at these types of A/F under WOT. When speaking of thermal management most engines have a wide window of A/F's that they will complete normal combustion under. But this window will shrink under WOT conditions even if the engine in question will run at 13.5 or the lower 13's as you posted earlier. It will not live long the additional thermal load placed on the motor will cause more stress over the life of the engine. The additional fuel will be used for thermal management within the cylinder. This is why I tune most of my N/A engines to the 12.8 to low 13's the small amount of fuel from 13.5 to 13.0 will not make the engine suffer a large power loss. In my testing under WOT and steady state load cell tuning the loss of power is very small if any between lets say for instance 13.5 and a 12.7.

Power is made with cylinder pressure (ignition advance) air fuels are a matter of thermal management not power.

Also in my studies leaner mixtures tend to create better throttle response not much of a power gain or loss. As long as you stay within the window of A/F's that a given motor likes and not to rich to cause misfire or to lean to cause a misfire the power output change is negligible.



Chris Macellaro

 

Hello,

You basically restated what I've said.

On top of everything a leaner car will be tempermental and spark knock easier than a car tuned a hair fatter. You can tune a car to 13.10's and it will be a baby at the track, be really consistant, and 60' good.. You can make a bit more power leaner but performance will fall like a rock when it gets a bit of heat into it and so on..

Let me also say that there is no magic AFR number.. 13.2 isn't perfect for all cars and I proved that a weekend ago with a NA car that preferred to be run in the mid 12's.

Theres a guy across the state that literally tunes everything to 13.5 and higher. You can go on his website and review his dyno sheets and see exactly what i'm talking about.. Most of them are actually in the 13.7-14.0 range. Its a wonder how he stays in buisness. I'm begining to think its catching up to him though as he is the butt of many jokes on the local boards.

 

Isn't 12.5:1 the best A/F ratio for producing power? It was in one of my books. Some local shop owner here thinks that 13.5:1 is the best power producing A/F ratio, but that seems like it would be way too lean on a WOT pass.

I know that 14.7:1 is the cleanest burning A/F ratio for idling, light throttle and cruising. Correct me if I am wrong, but I think that is why we have fuel injection, O2 sensor(s) and closed loop mode to make it possible for our V8s to get respectable gas mileage when not racing.

 

Nope it wasn't knock retard. Like you said all cars don't like the same thing. Mine didn't like going lean to hi 13s. It actually sounded worse lean than it did when it went rich into the 11s.

 

can you post a link to the site that is doing the melt downs?? I'm across the state line and I rather not find it the hard way.. pm if you wish. I think I might have an idea who and where just would like to make sure. pm if you wish. thanks mp