Brit Iroc

Hmmmm... This was its first test on the '87 350 iroc since installing the new cam and the ported plenum. Already had the Edelbrock runners, manifold, headers and the TFS heads. The chips been done by Ed Wright. Im using the stock injectors ( 22pphr) set at 47psi and Im thinking thats the problem. At 5500rpm the a/f ratio was reading 14.5/1. At that point the headers ignited some of the plastic shrouding around some of the wires and the sealant on the floorplan near where the Y pipe is!. The guys were quick and shut the motor down and put the fire out. I was lucky and there is no major damage and I drove the car home.
Would I be right in thinking now that an upgrade to 24lbhr injectors would be a good move? Also while Im doing that would it be a good idea to upgrade the fuel pump to a better one? I have a afpr on the car and thought it would be better set at around 50psi or is that not the best way to go.
I realise I will have to send the chip back to Ed for an upgrade with new injectors.
All comments welcome. Thanks in advance.

86camaro383

I would say screw the tuning, and worry about putting heat sheilds and reflective tape to prevent more fires.

mpilarZ281992

Interesting. Im not an expert by all means, but I dont think changing the injectors, fuel pump or psi on AFR would make a significant change at 5500 rpm. I would assume that you could benefit with 24 injectors with settings at 50psi, but in reference to catching on fire I say its pretty damn hot down there. Sounds like your running way to rich and may actually need a re-tune. Heat shields will help avoid fires. By the way, what header and Y-pipe system are you using?

Brit Iroc

Thanks for the comments. Im using the Edelbrock headers, ( ceramic coated would you believe!), and Y pipe. according to the AFR figures its around 14-1 at 3000rpm and getting leaner as the rpm rises. Surely it got that hot because it was running so lean?. Am I past the point where the stock injectors cannot keep up?.
The induction setup is K and N's, de-screened MAF, fully ported plenum, Edelbrock runners and manifold, TFS heads, Edelbrock headers and Y pipe, no cat and Edelbrock cat back. Its got a Comp cams 210 220 duration 480 lift with 112 lobe sep. Ed Wright chip.
Thanks again.

AutoRoc

If the pump can flow the volume, more psi=more fuel. I think I've seen 24lb'ers run at 80+psi in a 9 second N/A car. I'd assume that is 650+hp.. I'd crank pressure to it and see if it helps. It should!


Are you spinning it well past 5500? If you're looking for safe numbers..12.5-13:1 would be much safer and make more power. You probably know that though.

ws6transam

14.5 is still stoichiometric. It's not "too lean". However it's probably leaning out. If you were at wide-open throttle and running 14.5 then yeah, it'll make the pipes glow red.

If you are setting things on fire then you should also check for insufficient timing. Check your base timing, and make sure that when the computer says it's at 6 degrees, you are indeed at 6 degrees.

Also, what was the duty cycle running on those injectors when your AFR started inching up? Was it maxed out at 100% yet? You need to know before deciding to change the injectors. You should have your injectors hit about 85% duty cycle at peak torque through peak RPM to yeild a target AFR of about 13:1 to 13.5:1 for maximum power in a naturally aspirated application.

Lastly, if they are disc injectors, your maximum safe fuel pressure is about 50 - 55 psi. The OEM disc injectors can and will lock up at pressures over that, and that will quickly burn a hole in a piston before you know it's happening. It'll be ONE locked injector, and the other seven will happily sing while that cylinder screams it's death rattle. You might not even see it on the AFR gage either, as AFR is an average of all eight.

Rice Killer87

This right here is what you should be looking at to tell if you need bigger injectors or not.

Wrap or tie up those wires so that doesnt happen again and then take it back to the dyno or hook it up to a computer to see where the duty cycle is. If its anywhere near 100% than I would upgrade.

Brit Iroc

Thanks for the advice all. What I have now is EFILIVE V4. Also on the way is a Autometer wideband kit so I can keep an eye on the AFR. Can I use the EFI program to find out the duty cycle?. There is a section that ,I think, shows the injector opening times... stand to be corrected on that. Its titled 'BPW at last inj' and is in milliseconds. Any good to me?.
Autoroc..he revved it to 5500 but it was past its peak at about 4800.

I suppose it does not help with the injectors been 22 years old!!.
Thanks for the info. As you can imagine in the UK these cars are not that common so I'm on my own now Ive come this far with it!!