Misfire

[Spid]

Did a trackday at Spa on Monday, the Ult would do 3 laps happily then started to misfire/cutout. Let it cool down it would be fine for another 3 laps. Going to wire in a fuel pressure sensor to the dash to see if that's dropping. Any other ideas of what could be causing this?

[F.C.]

Poor heat management, you answered your own question really.

[spatz]

if you do that maybe add a temp probe as well would be really interesting !

[Spid]

Just was wondering what was getting hot to cause this?

[F.C.]

Put it on a rolling road and get someone who really knows about fuel and ignition to check things are ok there.

[Spid]

I hadn't thought of that, when it was first put on the rolling road they removed the rear clip. I was going to have a fiddle and take it up Brands and see if it was any better. Good call thanks

[MarkWebb]

I suspect you will find fuel pressure dropping due to heat in fuel as I did in the past. I have managed to cure it so far by pressurising the lp side of the fuel system to about 6 psi. This is to try to make sure that the suction side of the hp pump gets fuel and not boiling fuel. I was at spa as well as you know. The most I managed was 6 laps due to oil temps getting a bit high. No problems with fuel pressure though.

[F.C.]

Heat wrapping fuel lines, protecting fuel tanks, with reflective film or paint (NOT black!!) ceramic coated exhausts, heat shielding on HT leads etc, will go a long way to improve your heat management.
Racing teams fight to keep the fuel cool to (a) improve the density and (b) to get more fuel in the tanks.

[gyroplane]

Have you read macgtech's writup on their recent experience at the Silverstone 24hr?

http://pistonheads.com/gassing/topic.asp?h=0&f...

Lots of discussion about LS7 misfire (with potentially devastating results), possibly related to heat (or fuel?).

-Sky

[Spid]

Interesting, might be worth trying the regulator before the fuel rails

[F.C.]

Get rid of the problem, if you are having to stop and wait for it to cool you have a heat issue, upping fuel pressure may well improve things initially but you will generate even more heat, something WILL give in the end.

[MarkWebb]

Whats the problem with my solution? It is recommended by Kinsler in this article http://www.kinsler.com/Cat_32_Pgs/Cat_32_4_09_Pg_1... Just do not set pressure valve on lp side to more than the lp pump can provide or you will be stuck with vapour. A small hole as a restictor was suggested because vapour will pass easily but liquid fuel will not so creating the required pressure in lp side.

[F.C.]

Nothing wrong, just getting rid of the heat problem is better practice, less heat = better fuel density.
If your fuel is getting hot cool it.
use a small cooler on the return to the tanks.

[Spid]

Its in bits, going to get exhaust coated use some heat shielding on the tanks and fuel lines. Also going to try to to add a bit of pressure to the swirl pot. Mark what do you use to do this?

[Spid]

Its in bits, going to get exhaust coated use some heat shielding on the tanks and fuel lines. Also going to try to to add a bit of pressure to the swirl pot. Mark what do you use to do this?

[Spid]

Its in bits, going to get exhaust coated use some heat shielding on the tanks and fuel lines. Also going to try to to add a bit of pressure to the swirl pot. Mark what do you use to do this?

[Spid]

Its in bits, going to get exhaust coated use some heat shielding on the tanks and fuel lines. Also going to try to to add a bit of pressure to the swirl pot. Mark what do you use to do this?

[Spid]

Its in bits, going to get exhaust coated use some heat shielding on the tanks and fuel lines. Also going to try to to add a bit of pressure to the swirl pot. Mark what do you use to do this?

[Spid]

Its in bits, going to get exhaust coated use some heat shielding on the tanks and fuel lines. Also going to try to to add a bit of pressure to the swirl pot. Mark what do you use to do this?

[Spid]

Its in bits, going to get exhaust coated use some heat shielding on the tanks and fuel lines. Also going to try to to add a bit of pressure to the swirl pot. Mark what do you use to do this?