The V8 Owners Forum -

At the last meeting the car was loving the gas and extra grip from sticky rear MTs.

Didnt go quite as well this weekend with a rained off Sunday. Monday was better and the track was getting better all day.

But i had the return of the dreaded backfire on a NSCC qualifying run. The explosion from the plenum completely blew apart the air filter and even blew the 72mm plenum sleeve out of the plenum intake

So on the following 2 runs i used only 1 stage each. I used stage 1 with a 70 shot at full throttle and ran 12.2 @ 114 and the wideband was in the 13's so maybe a little leaner than i would normally like. On the next run i used stage 2, a 100 shot on a pushbutton and ran 11.9 @ 119 with the wideband dropping into the 10's so all fine there.

But then i had a tough race to face and had to deicide wether to risk using both stages......

Here is the in car video

http://www.youtube.com/watch?v=DU2-o2uGQG0

Same damage as before but it all went back together and i drove the car home. it seems fine but i will at least pull theplugs and do a comp test etc.

Doesn't seem uncommon if you look for Nitrous Explosion on youtube!!

Perhaps your inlet valves are a bit burned and allow the explosion to pass back into the inlet manifold.

Chris.

Tell us the procedure you are using Del??

1st stage fixed hit on wot switch in all gears??
2nd stage fixed hit on button in each gear??

I've only ever had one backfire on track. And it blew the bonnet off its hinges. But I know why it happened. The engine was ok and I went on to race the rest of the day with no issues luckily.

You seem to be shifting around 5500rpm which I think is a bit high for making best use of the torque you have. But thats not the issue eh??

Are you sure that you came off that button fully between gears??

I would be interested on your theories Pel.

On that run i had 70 bhp at WOT. Barerly touch WOT in 1st but then full on in 2nd 3rd and 4th for the second 1/8th
The pushbutton had 100 shot, i gave it a blip in first then was full on in the other gears. The backfire happens as i am midway in 3rd gear before the 1/8th. I come off the throttle and the button but am aware that Ian is not far off in the left lane so i hit it again and get the second burp. The rest of the run was on just the 70 at WOT but i had slowed too much and Ian came by at 123 to my 103 over the line. Only beat me by a tenth

As either nitrous is activated a signal is sent to the Megasquirt2 ECU and it immediately switches to a second map that is retarded 6 degrees.

I plan to only use the pushbutton stage with a 60 shot in the future and use it for the road or as an emergency back up if required.
The other system will be jetted for 125 shot and the max extreme controller will be wired in. Some progressive control will be welcomed along with features such as nitrous delay etc.
I have no excuses time wise now i suppose (being a doley) so will get it all sorted before the return to Yoyk on 8th July.

dbv8 wrote:even blew the 72mm plenum sleeve out of the plenum intake

Is that one of my 72mm plenums? Some of them are welded on, but more recently i simply press them in with some locktight.
For what you are doing, you should have a couple of spots of tig on it or make a bracket to support/hold it in.

Yoyk ???

You living in Chigago now ??

Do you have any way of logging the ign retard ???

If the problem happens at the same time on each pass there must be an issue with the timing and fuelling in that 3rd gear time zone??

Can you re map your retard yourself ??