Hey guys, I posted this on the power adder board, but chargers and turbo's on TBI setups doesn't seem to be a common combo Needless to say, I couldn't get much help.

Here's my problem: My car seems to be more powerful at part throttle than at full throttle, and I was doing some research and discovered that my car can "learn" fuel maps at part throttle and compensate for any flaws, but at full throttle it resorts back to the default maps. I think that all the extra air flow is confusing the computer to much.

I also found out that the major supercharger manufacturers make carbs that are prepped for a centrifugal charger's boost.

Also, a question for you guys who have burned chips for TBI cars: Is it difficult to do? How long does it take to learn the software and become efficient in it's use?

So, Do you guys think I should catch up to the learning curve and invest in the chip burning equipment; or should I replace my TBI setup with a carb and a new manifold?

Thanks for any help guys,
Matt

sweet ride, btw. Yes, the computer goes full rich (12.5:1) at WOT to prevent you from burning things down and because the o2 cannot respond fast enough. When the computer does this, you are definatly goiung lean. Also,t eh maximum fuel that the stock system can provide isnt that much so that probably does it too. Good palce to go is the DIY Prom board. Very knoledgable bunch of guys over there.

Thanks for the compliment on my car I'll give a try over there to see what I can come up with

Matt

The ECM shouldn't just run from stock tables at WOT. I believe the WOT enrichment is based on the part throttle BLMs. So if the ECM has to run richer at part throttle, it'll run that much richer at WOT. Perhaps your fuel system is not up to it (namely the fuel pump or injectors)?

That was another idea. I have a secondary fuel pump on my setup, and it keeps me at a steady 16 psi, even under boost. If it isn't the fuel tables, my next guess would be the injectors, or the restrictive TBI or manifold. What would be the best method to determine what the problem is with out replacing the parts?

BTW: I tried reading the voltage on my o2 sensor, but I couldn't get a steady reading. So, I was also going to replace that and see if that improves my situation any.

The o2 sensor will never give a steady reading. Its always compensating quickly for only two conditions LEAN or RICH. The reading will fluctuate like mad under idle, but at WOT, then you should definitly get 1 consistent reading, either a lean case or a rich case, but at WOT, its almost always gonna read lean unless its a pure stock setup in which case is just about right for the engine's flow capabilities on the table.

ok, that is what it was doing. I guess now I HAVE to hook up my multimeter again and go flogg on my car

Actually it's worse than that.

The WOT mode only changes the A/F ratio to 13.2:1. So it's running even leaner than 12.7:1.

AJ

Let me see if I can ask a few questions and maybe give you an answer. Note: I ran a Paxton (YUCK) Supercharger on my 350 TBI truck for 4 years and did lots of tuning on it.

1. Are you using only your factory injectors to supply fuel to your beast or did the kit come with some additional injectors to run on the system?

2. Have you setup a Winaldl system yet so that you can monitor all aspects of your car? Not just the AFR. Knock counts can kill your horsepower if it is retarding your timing tooo much.

3. Is the 16 psi fuel pressure being controlled by the stock regulator or do you have an after market regulator?

I would try and get the writer of the Win ALDL software to try and help you. He has a blower set up on his 350 XFire Vette which he has done various things to get running right and make good power. Naturally, he burns his own proms so I don't think he'll recommend a carb. His username eludes me at the moment though. Anyone? If not do a search on the DIY PROM for Win ALDL and I'm sure you'll find him by his sig.

Hey BHarris, I got some answers for ya

1. I still have the factory injectors, but the system does have an FMU. What that does is it boosts the fuel pressure by causing a restriction on the return line.

2. Me and my dad hooked it up to a scanner, so I could verify that there was no knock. But I am going to make the interface cable today to run one of those freeware monitoring systems. That way I can see how bad my fuel maps and such really are

3. It is the stock regulator, but the FMU regulates the fuel pressure under boost.


Hectorsn, I think his name is Jonas Blund or something like that. When I was still in my planning stage of the project, I did some research off his site. That is a pretty cool looking bonnet he has for his TBI. I'll throw him an email and see what he says.

Thanks for the help guys, and keep it coming

1. I don't think the factory injectors are going to provide near enough fuel for a supercharged engine even with increased pressure. The paxton kit came with 2 40lb/hr injectors that ran in a spacer under the TBI that a paxton computer controlled. I think it would run better if you replaced stock injectors with 85lb/hr 454 tbi injectors and replace the stock pressure regulator with a vacuum adjustable regulator that would decrease pressure at idle and increase it all the way into boost.

2. I would think you would be getting at least some knock. I can't keep my nearly stock 305 from knocking with standard 0* base timing. 305's just knock a lot. When I first stomp the throttle I will get around 5 knock counts using winaldl. My 350 didn't knock but 1 or 2 knock counts with the supercharger running on it. I ran the stock 0* timing on it with boost retard on the timing. Retarded 1* for every 2psi of boost and I was running an 8psi kit.

It takes a while to get those things dialed in. It is not as plug and play as they made it seem. Also, did you change your valve springs when you changed the cam. I found that I had to run stronger springs because the increased cylinder pressure from running under boost caused the valves to float about 500 rpm before redline.

I got some more numbers here to, if that helps any

At WOT the oxygen sensor is about .720 but at steady speeds it stays about .890

fuel curve (integrater) stays close to 128 on the highway, but at idle it was goin as high as about 134.

My car was picking up a couple knock counts, but we think that it is just "noise" from the SC that it is picking up. So I temporarily disconnected the sensor and wired a resistor in it's place.

I see what you are saying with the injectors, but I was told that I can't upgrade those until I get the prom burning equipment, otherwise I will run filthy rich. Also, those are upgraded valve springs

Thanks for all the help you are offering BHarris,
Matt

Edit: About the knock counts, keep in mind that my setup is intercooled, so my intake charge isn't as hot as a standard SC would be

On the injectors, you can run 350 injectors and not have to mess with the computer. I run them in my 305 with the mods that are in the signature above. My blms run right at the 128. I noticed that it would drift rich at idle so I adjusted the chip a little but it wasn't absolutely necessary. I just did it while I was practicing some chip burning and removing the 108mph speed limiter on my convertible. The 350 injectors may not completely cure the problem but should help. They are rated about 15# more than 305 injectors. You can get the whole 350 TBI pretty cheap out there on ebay. I think I paid $40 for mine just so I could get the 350 injectors.