andrew

Hi Guys,

I had a local tuner map my car on the dyno and I am very happy with the figures. Its not making a lot of boost even with a 17% reduction pulley so I don't understand why it stops making power over 6k. On the road it feels like I am hitting a 'soft limiter'. Revs increase but at a slower rate than under 6k and it sounds different too. I am thinking it could be the spark. I have changed the plugs to colder plugs when mapping it and the gap was decreased as it was blowing out the spark. I am using standard coils and leads. I have checked overboost protection and boost control setting in tunerstudio but these are set to off and 200kpa so should not be effecting it.

After the dyno session I changed the injector to EV14 550's. DC were half of what they were but the problem remained.

If anyone has seen this before and has some suggestions please post.

Oni

iTrader: (1)

Your losing boost at higher rpms, probibly a boost leak would be my guess but im a noob . Id get TS and VEAL your fuel table aswell, your afr is allover the show. Stock ignition is fine at your boost level maybe run one step colder plugs. but yeah fix what ever is making u lose boost up top wouold be interesting to see a torque plot, it probiubly drops off fast at about 6.2k rpm and thats why it feels odd.

Pro's.. am i atleast close ?.

Thanks
Scott

andrew

Thanks Scott,

Both my msq and dyno show I am losing boost over 6k, but why would i only loose it over 6k if this was the cause. If it holds steady up to 6k i don't see why it will leak over 6k.

Also the dyno graph of AFR is a bit rough it uses the dynos O2 sensor, but my msq's are steady at around 12.5 AFR all the way through boost. Torque does drop off at 6k too. I will post the torque graph later.

triple88a

iTrader: (2)

Man you're loosing over pound an a half of boost after 6k rpm.

Oni

iTrader: (1)

Had a look at the log and my untrained eyes cant see anything funny. Your sig says cat back exhaust, are the headers stock? could it be the exhaust is too restrictive at higher rpm?. Just throwing out ideas interested to see what the solution is for you.

GL

triple88a

iTrader: (2)

Naaah man highly doubt it, is there something happening with the timing or physically inside the SC?

Is there a valve or something that's kicking in your supercharger?

I'm guessing a boost leak will be gradual as rpm goes up, not a 1.5 psi jump in 200 rpm range.

andrew

I need to update my sig. I have ebay header to catback and full 2.5 stainless after the cat back.

The only valve in the system is the mini bypass valve. It reads vac from the intake manifold and closes (I think) under boost.

I'm thinking its a timing or spark problem but I might tighten the belt just in case its slipping at higher rpms.

Braineack

iTrader: (62)

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andrew

Thanks for your post Braineak, I dismissed this advice at first as there was no belt slipping sound from it over 6k and it felt like it was tight enough when comparing to another car. However I had a spare belt and to eliminate it as a cause I tightened up the belt.Took it out for a test run and noticed it was much better. I haven't really tuned it over 6k, so turned on laptop and did some autotuning.

Its much better ! Boost now builds all the way to redline. Its a beast.

Ben

iTrader: (33)

Restrictive exhaust would actually increase the boost, as with the M45, boost is a measure of restriction.

Slipping belt is the most likely explanation.