Hi there forum folk.

I have a 2018 R with the VAP tune, downpipe and dual (upper, lower) pulley. The car is currently on 25k miles. Newish Michelin Pilot Sport 4 S 305 tires on the rear. 1000mls since last main dealer service.

Since the upgrades, the car has consistently been slipping/bouncing off the higher range of revs when pushed really hard. As I very rarely push the car, it is not too much of an everyday issue. But this morning on my way to work I was stuck behind a very slow-moving truck. When the road opened up to a dual carriageway after a set of lights, I floored the accelerator and roared off, passing the truck, only to hit the red line in 2nd and bouncing off it, causing a momentary stutter but enough to stop the car accelerating.

The road was dry and the outside temp was c.10C. The car was in s mode.

I would appreciate any feedback or experience that anyone might have. I have reached out to VAP but have not had a response.
I didn't get a chance to do a before and after dyno but going by what VAP have said, the car is somewhere in the region of 100bhp better off. I read somewhere on this forum that a car may need colder spark plugs with this amount of increase in power?

Apart from this issue, everything else is great. It's a proper jekyll and hyde car.

 

If you are "bouncing off of the rev limiter" and it is hesitating, that is working as it is designed. This will have nothing to do with plugs, or anything else.

The issue will be why it is hitting the rev limiter? Is it not shifting prior to hitting the limiter? Are you paddle shifting, and holding it too long? Did you get a TCU tune with the elevated limit?

Best to hear from Chris from VAP on what may be going on with the tune.

DC

 

Would AT car not shift at the red line regardless of mode you are in?

 

I’m no expert but when in sport mode and using the paddle shifters it will not go into a higher gear without manually using the paddle shifters or moving the gear shift. It will bounce off the rev limiter until you shift to a higher gear, ask me how I know. That’s the genius of sport mode it acts like a manual without the third pedal. I love it!
Frank

 

Yes...That is correct In Sport Mode when you paddle shift, it will hold the gear regardless...That is one of the reasons I was asking about him shifting manually.

Also, on a stock engine, the CAN bus is able to keep up with the revs, and shift appropriately, but sometimes on tuned cars, it cannot, and thus hits the limiter before it shifts.

DC

 

Been there. Done that. Engine sounds awful bouncing off the rev limiter.

 

Thanks for the replies guys. The car is always in auto when it happens. I haven't actually tested to see if it happens when paddle shifting.
Since last week and because the weather has been so nice I have tried to replicate it and it seems very consistent. I will try to get a video of it somehow to show. But it appears it is not bouncing at the redline but just below it. When I hit the accelerator hard the auto drops a couple of gears and it is at this point it bounces around.

Is there a way to contact or tag chris@VAP through the forum. Newbie I'm afraid.

thanks

 

I have managed to get a video of the issue. Nothing a bit of sticky-backed plastic cant sort!

This was using about half to three-quarters acceleration. In sport auto.

 

Thanks for the video...That really does look/sound like ignition honestly...Why? Because it is perfectly smooth, until it holds at mid/high rpms. I certainly could be wrong, but the way it sputters just looks like a spark issue? Maybe a bad, or improperly seated coil? Or even a bad or wrong plug(s).

Would seem if fuel related you would have sporadic sputtering, b not just at the top of the powerband? Just my thoughts...

Good luck with it.
DC

 

Do you think it would be worth changing the plugs regardless?

 

If it is ignition related, it could be a plug or coil (if it is a specific cylinder - need to check OBD Dx or data log). If you do get a misfire error...the next appropriate step is to switch that coil and/or plug with one from another cylinder to see if the misfire moves. If it does, you have your answer. You want to move one at a time (coil or plug), not both, because then you do not know which one may cause it.

DC

 

If it was a plug issue, then I would expect the suspected plug to play up throughout the rev range, maybe in the maximum load range or possibly down low, but not in such a tight rev band as the engine seems to come 'back on song' after 6400 rpm for a short period.

1600 - 5500k it is sweet, it's as thought the rev limiter has 'slid down' the scale to me.

I'd put my money on the ECU telling the engine to cut back at those revs because it's not a happy bunny, BEFORE reaching the actual mapped rev limit.
Air, fuel, boost, who knows without looking at the data?

Shame you cannot get through to VAP, be interesting to find out...I am most probably wrong...I was, once before ;-)

 

Does that issue occur in that rpm range regardless of load (throttle position)?

 

The higher the load the more 'jumpy' it gets. At max load (pedal to the floor) the car is quite violent in that rpm range!

 

The first map i had was even worse. Chris said " the previous file was just demanding WOT earlier on versus now scaled more towards pedal demand".

Think i will try and reach out again.

 

It certainly sounds like a bad coil.

 

Thanks for the advice everyone. Will try and get a garage to look at it for me.

 

Did this issue ever get figured out? was the issue because of the pulley tune?

 

Resolution? Don’t just leave us hanging lol.