Speed cut?

[knockoutgiant]

Okay so, I was at the Manfield track yesterday for the trackday, for the most part my BL went find! However towards the end, for the last two races, I got onto the main stright, hit about 165kph and then she just stopped... It was like it was misfiring, or hitting speed cut or something. There was easily enough fuel, and only happened in 4th on the main stright, any ideas?

[Fastfour]

How did you test it on the way home?

[lachlan]

yeah edit that line out of it

are you certain it had enough fuel in it ?

wonder if coils or something were getting hot ?

[Guest]

Chinese walbro?

[knockoutgiant]

 lachlan said:

yeah edit that line out of it

are you certain it had enough fuel in it ?

wonder if coils or something were getting hot ?

What line?

Anyway, yup, sure it had enough fuel. Just below half and even if that was the case, surely it would have been happening on the corners more than the strights? Also, pretty sure it\'s on the stock fuel pump.

[Jesus]

 Fastfour said:

How did you test it on the way home?

Accidental wheelspin on a spot of diesely BP forecourt officer. Honest.

[Johnnynz]

Temp cut? Was pretty darn warm out there yesterday.

My temps were the hottest I have ever seen them.

[knockoutgiant]

 Johnnynz said:

Temp cut? Was pretty darn warm out there yesterday.

My temps were the hottest I have ever seen them.

That would be my guess, wasn\'t sure if we have anything like that in our cars though? It never got too high to actually worry about which was good.

[Marky]

Not at 165k

Wonder if its just the speed cut coming in a bit early, maybe the needle is way under reading? (Mine shows about 8k faster than the ecu sees @ 100kph for example)

Another thought is what boost is it running, might be just high enough to trigger a boost / load cut with the higher loading up

Only other thing is do you remove your headlight or have a ram air setup of any sort?

[knockoutgiant]

 Marky said:

Not at 165k

Wonder if its just the speed cut coming in a bit early, maybe the needle is way under reading? (Mine shows about 8k faster than the ecu sees @ 100kph for example)

Another thought is what boost is it running, might be just high enough to trigger a boost / load cut with the higher loading up

Only other thing is do you remove your headlight or have a ram air setup of any sort?

Nope, headlight stayed the whole time. Also, mine reads about 5-8k too fast (according to GPS) and surely if it was boost/load related it would have been happening in all the races, not just the last few? I did have a cat-back exhaust on which may have made the boost creep up a tad.

[Johnnynz]

 knockoutgiant']

[quote name='Marky said:

Not at 165k

Wonder if its just the speed cut coming in a bit early, maybe the needle is way under reading? (Mine shows about 8k faster than the ecu sees @ 100kph for example)

Another thought is what boost is it running, might be just high enough to trigger a boost / load cut with the higher loading up

Only other thing is do you remove your headlight or have a ram air setup of any sort?

/quote]

Nope, headlight stayed the whole time. Also, mine reads about 5-8k too fast (according to GPS) and surely if it was boost/load related it would have been happening in all the races, not just the last few? I did have a cat-back exhaust on which may have made the boost creep up a tad.

Markys much much smarter than me at this and can probably provide a better answer but different weather conditions will produce different boost levels. If you had an increase from exhaust and were right on it all day a decent bit of a breeze coming up might have created the right conditions to push you over that cut threshold.

I noticed an approx 2 PSI difference in sessions throughout the day dependent on when that breeze was up and when it wasnt.

Did you have a boost gauge to keep track?

[knockoutgiant]

 Johnnynz']

[quote name='Marky said:

Not at 165k

Wonder if its just the speed cut coming in a bit early, maybe the needle is way under reading? (Mine shows about 8k faster than the ecu sees @ 100kph for example)

Another thought is what boost is it running, might be just high enough to trigger a boost / load cut with the higher loading up

Only other thing is do you remove your headlight or have a ram air setup of any sort?

/quote]

Nope, headlight stayed the whole time. Also, mine reads about 5-8k too fast (according to GPS) and surely if it was boost/load related it would have been happening in all the races, not just the last few? I did have a cat-back exhaust on which may have made the boost creep up a tad.

Markys much much smarter than me at this and can probably provide a better answer but different weather conditions will produce different boost levels. If you had an increase from exhaust and were right on it all day a decent bit of a breeze coming up might have created the right conditions to push you over that cut threshold.

I noticed an approx 2 PSI difference in sessions throughout the day dependent on when that breeze was up and when it wasnt.

Did you have a boost gauge to keep track?

I wouldn\'t have thought a breeze would be enough to give an extra 2psi And unfortunately I don\'t have a gauge to keep track of it

[Johnnynz]

I\'m not very good with Link but I will try grab my intake temps and chuck them up tomorrow or next day. I had significant differences in Intake temp across the three sessions when I looked last night.

I\'m probably running a bit more boost than you so I guess more room for variation and I had a small boost leak issue so 2 PSI might be a representation of that. But I know my setup has a decent variation in peak boost based on intake temps. Not sure if the stock setup works that way.

Without an idea of the boost being run its a bit hard to know if boostcut is a possibility.

[knockoutgiant]

 Johnnynz said:

I\'m not very good with Link but I will try grab my intake temps and chuck them up tomorrow or next day. I had significant differences in Intake temp across the three sessions when I looked last night.

I\'m probably running a bit more boost than you so I guess more room for variation and I had a small boost leak issue so 2 PSI might be a representation of that. But I know my setup has a decent variation in peak boost based on intake temps. Not sure if the stock setup works that way.

Without an idea of the boost being run its a bit hard to know if boostcut is a possibility.

I did dyno it and it was running 15psi tapering down to 12psi at redline, but of course that\'s in Speedtech cold, windy dyno room, and the stock exhaust, not out on a hot track with a cat-back on haha