95 LTI Camaro

[Randy Wells]

Just to show I am not all political, I need some advice something me and Bob never ask for, kind of figure it out as we go.

We have always run SBC’s with carburetors, 67 D/S 302 Camaro, 68 350/295 F/S Camaros, always built our cars and Engines, Last year we bought a 95 Camaro LT1 car with 2 pedals ouch, from Div 1 had a good history, and the price was right, and we just did not have the time or energy to build one from scratch. Were happy with it but it was a dog from the beginning, supposedly had a fresh motor. Bought it in February so had to take the sellers word on it, and the 2 day drive didn't think of doing a leak test on it. Car run 3 under in the spring at Topeka using the tune that came with it, knew we had a problem, tried some stuff and picked up just a little. Bob had enough, so we pulled the Engine and built a new motor, tore it down it had .012 piston to wall, and a couple of valves were leaking, bought a set of not so cheap heads from one of the best Stock head guys, CP Pistons, the latest Total Seal Ring Package, Comp solid Rollers, Comp Lifters, picked up a couple more with the same tune on it, but we know there is more in it. My question is if we take it to a hub Dyno, Patterson’s guy in Wichita, what can we expect to see as far as performance from a good tune. We are currently running closed loop, Alpha N Mode, think it would be faster in in open loop Speed Density Mode. The ECU is a FAST 2.0 Thoughts/Advice. I am a I&E guy and can get into a Process PLC and set High Alarm and High High shut downs, and no some programming but this stuff is wearing me out.

Thanks

Randy Wells
C/SA 5034
Wells Bros

[KRatcliff]

Closed loop/Alpha N is a little odd. Normally they are Open Loop/Alpha N which is what I would run, but that is me.

[Randy Wells]

I checked the tune, we are running Alpha N Mode, so we are running open loop, what little we were told about these FI cars, is we should run close loop Alpha N Mode, until we get a good tune to keep from hurting the car, because it auto corrects the A/F, is that correct? Sounds like we got some bad information.
So the tune that was in the car, is set up for east coast track, I know the guy run Atco a lot with it, well our weather is completely different, Bob took it to Topeka last weekend in, 4200 DA it was hot, said car was not liking it.

[KRatcliff]

It is a personal preference, but I don't want the ECU correcting the tune on my cars going down track. Some do like it this way, but I don't at all.

The A/F ratio you would want to target is somewhat dependent on the fuel you are using and sometimes the current O2 sensor in the car. They all seem to read a little differently. For example I run VP C11 and my car seems to like the 12.8 range.

You could be anywhere between 11 and 14 on a pass and I don't think you will hurt the car due to the limited time you are going down track. I doubt you are that far off in the first place since it was running at other tracks. You are probably pretty rich. I would put it in open loop and log it then target somewhere in the 12.8 to 13.0 range. The car will tell you what it likes on the time slip (or time slip app).

You may be able to get it to where all you do is adjust fuel pressure depending on the track. I would start with my fuel pressure at 52 lbs or so with a 4,000' DA. That should give you some room to drop it if needed on a worse DA. I don't like to run less than 50 lbs of fuel pressure.

[BRETV]

We always go back to open loop speed density and monitor A/F ratios and adjust fuel and timing accordingly. I know many people will tell to you run closed loop and let the computer do all the adjusting, we were carb guys too and like to make the changes ourselves, we're old school. LOL. We have learned on the FFFords, they like less injector with more pressure and if the A/F gets rich at all, it really slows them down. Just my $.02 Good luck with it.




Bret Velde
2003 FS/??

[Rich Biebel]

I built one in 2006 and had zero experience or knowledge about tuning an EFI engine. Never even ever saw an LT-1 engine ! I had an Accel Gen VII ECU and ran it in speed density, bank to bank and closed or open loop really had very little to do with performance. I bought a stand alone data logger but got nowhere with that.

I should have done a dyno session with an experienced EFI tuner. Would have saved my self a ton of time and aggravation. I was stubborn and wanted to learn it and used a hand held A/F data recorder (Inovate) to get it working reasonably ok.......I ran some 10.50's at nearly 125 in AF/IA at the time.....about 150-200lbs over weight for the class....

Atco air is very fast in spring and fall......I ran 10.50's there at one event and it was way below sea level.....-1000' DA in the morning !

A good friend still owns the car and owns a second one. He's run some 10.20's-10.30's at 128 in one car and my old car has run close to that at one time.......At Atco.....and maybe some other tracks in real good air

I drove my old car at one event and in B/SA at 3200+ lbs it was going 10.50's in good air. They fall off pretty bad as the air gets far worse.
They do like to be cold......and will pick up a lot.....

I think on the dyno some power was found running it in Sequential but really not much and not really anything on the track.

A pretty good one makes around 500hp on an engine dyno or so I've been told.....

They are great cars to race AFTER someone very experienced tunes it or schools you on how to work with the ECU you have....and you have a good working knowledge of how to make some changes.

[Signman]

You are doing the right thing running closed loop in either mode it will get you in the ball park without loosing a good engine. Watch the correction and adjust the table accordingly until less than 5% then you can run open loop and correct manually if you choose. The reason most don't like closed loop is sometimes the adjustment will slow the car when the table is good. Also remember the processor is making calculations which take time therefore the inaccuracy due to the correction applied later in time at the wrong cell. It's your choice as you become more comfortable.


My advice is to take the car to a good chassis dyno hub or not as long as the tuner is good and familiar with the combo. Doing it at the track will take a lot of runs. You can test fuels determine optimal timing and get the table set to make the most power and be safe in one day. You will still need to tune at the track due the difference in load. The dyno will apply similar load but there are a lot of variables so this is just part of it.

The AFR you end up as optimal will be determined by fuel, air flow/heads/intake, combustion chamber, squish, and the position of the O2 Sensor. The further down the header more lean will be optimal which is why asking for a number from others may not be helpful. Believe it is optimal to have the O2 within 18" of the exhaust valve. Pick the most lean or rich hole checking plugs consider the location for bung placement or run all eight.

Have heard these engines like as much as 13.2 AFR but again this may be dependent on how much fresh air the sensor is seeing which is a reason to not put it in the collector it will work and the car will perform either way. I don't believe the header is not pulling fresh air are high RPM there will always be a small amount and this can be true closer to the exhaust valve therefor the variable on the optimal O2 for your setup.
Also the O2 sensors don't last forever when your data log doesn't look right change it they can last several seasons or several per season. Leaded fuel is a big part of this. Don't drop them or bang anything near them.

[Randy Wells]

Thanks everyone for some good advise, we will be putting the car on a Hub Dyno when I get back from ND, This guy is in Wichita and came highly recommended by Alan Patterson. Hopefully can learn a little bit about tuning.

Randy