Running out of steam over 4.5K

[Howlin_Mad]

It's a Mk2 V6 with a rev 3 tubby box with LSD.

Pulls very well but seems to lack any go over 4.5K ish. The rev counter has been calibrated correctly as i'm seeing 3K at 70mph on the sat nav but it's performance certainly tails off over 4.5 whereas my mates V6 with the N/A box just pulls to at least 6K much harder (even accounting for the ratio's of the box difference)

I read a post on here somewhere (Gwrinkle i think) about poor dyno results and the problem seems similar (even though that was an N/A box i think) but i checked for the coilpack problem he was having and it's not that.

Any ideas?

Kieren

[OlberJ]

What's the script with the exhaust chief, is it still as when u picked it up?

[Howlin_Mad]

What's the script with the exhaust chief, is it still as when u picked it up?

Yes mate - i know it's not ideal at the moment but wouldn't have thought it would make THAT much difference. My mate has a Rogue conversion on a Mongoose N/A and i still have the Tubby Japspeed with the de-restricted t-pipe.

Although i have a 2nd front bank manifold now so i'm having that put on the rear bank and 2.5" tubing down to the Y-collector of the Japspeed exhaust to quieten it down a bit!

I Don't believe all this lack of back-pressure crap on road cars with std manifolds and a good exhaust length - just that accounts for a silly loud exhaust!

Kieren

[Paff]

The exhaust things are weird. I had a bike exhaust on mine and it gave too much back pressure and wasn't the greatest, infact when the clamp gave way and the silencer was removed the car ran sooo much better it was unbeliveable the difference it made. I think its a case of trial and error until the best option works.

[oddball]

Have you checked the acis is working properly? I think i am right in saying the actuator is supposed to open at about 4500rpm to provide better top end power. May be nothing to do with it, but its gotta be worth a look. quickly rev the engine over 5k and watch the actuator to see if it moves.

[Paul Woods]

One of the main things that can account for a lack of top end performance is fuelling,if the car has a weak pump it will tail off under higher loads.Thats just a possible though,don't take it as given.

[OlberJ]

Aye but run a 100 metres breathing in and out as hard as you can and you'll knacker yourself more and sound like a tit. lol

Why is it that when you get a blow in the exhaust there feels like it's got no power, and is blowing out it's own arse, is that purely a lack of fuelling/timing?

[oddball]

Run 100metre's? Thought thats what mrv6's are for, so you dont have to!

[Howlin_Mad]

Have you checked the acis is working properly? I think i am right in saying the actuator is supposed to open at about 4500rpm to provide better top end power. May be nothing to do with it, but its gotta be worth a look. quickly rev the engine over 5k and watch the actuator to see if it moves.

I'm assuming that's on the end of the upper inlet plenum? I'll check that tomorrow at work - i don't think my neighbours are overly impressed with the exhaust as it is - let alone me revving it over 5K on my drive rotflmao

It's running a Walboro 255 so i hope the pump's not faulty or anything - but could it be the standard ecu map now ive fitted a new exhaust and air filter setup?

Kieren

[Steve-x-edge]

I've got this exhaust so would be interesting to see how this turns out, and mine for that matter if there is any difference between mine and Kierens.

Steve