Folks, can you tell me, do Rolling Roads always show/make less boost than the car does on the road?? asking because mine was Dyno'd recently and it could only hit 1.79bar @ 341bhp/338ft/lb and yet on the road it's peaking @ 2.1bar, WHY??

I know of a few cars doing this also, cossie4i for instance..

 

Mine aint such a big difference though Pete.

Hits about 2.15 on the rollers and 2.3 on the road.

Steve

 

Mine was/is, can't understand it Steve, does it matter what gear they're ran in?? surely running it in 4th rather than 3dr holds better boost??

 

Done two runs with my car, 3rd then 4th

3rd gear made about two bhp more and a tad more boost too


Luciano

 

But does yours make more boost on the road dude??

 

Depends what the ramp rate on the rollers is set to.

 

is it the rolling roads boost pressure guage telling you the boost when your on it or your own boost guage.If its the first case maybe the rolling road boost pressure sensor is more accurate than your own guage as i dont think these are ever really that accurate

 

and its colder air most of the time when your on the roads too

 

As said most likely just down to different gauges some being more accurate, for best accuracy runs should be in 4th as this is direct(1:1) on most cars, being in a different gear will drastically alter readings as will different tyres pressures.
tabetha

 

bit of wheel spin maybe

air flow will make a small difference as the atc will be higher

 

Mine was .3 bar down on the rollers

 

I've got a GGR gauge and that reads pretty much what the RR printout shows.
tabetha

 

how about me then guys my car is mapped for 2.2bar and only makes around 1.6bar somewhere its losing boost as thats all it makes now road or rollers

ive changed the top boost pipe as it had a hole in it ive proper sealed the hose, but still only 1.6bar (although a mates t4 equipped car still cant catch it lol)

ive found that where the exhaust manifold bolts to the turbo when i start it up it slightly leaking would this cause it to lose 0.6bar (as said its slightly leaking)


any thoughts guys

 

Thats is one of my big problem that have to overcome when the car goes back together as mine always come loose due to the suspension setup - if anyone has any solutions to this issue please post up

From above mine was 70bhp down on the last rolling road and later found 2 bolts missing, 1 other all most out and the other loose but still made 371bhp

 

with my car when you turn it off there is like an air leak hiss for about 5-10 secs then its fine so makes me think its leaking on the inlet side somewhere ..... but like i said the manifold leaks where the trouser section meets the manifold

but still made 414bhp and 416lbs with 0.6bar missing lol
and my gauge reads the same as power engineerings rollers

 

Have you checked your intercooler for leaks ?

Sprayed all hoses, inlet manifold etc ?

Steve

 

Mine runs 34psi on the roads but last time on rollers it onlt hit 27psi and they run it in 3rd gear i also thought 4th would have been a better gear to run it in.....

 

i always used think this but with dyno dynamics most runs are done in 3rd??

 

That's EXACTLY the same as mine Lawnsy, i'm not worried now tbh as i know the engine's healthy and it goes like fook on the road which is where it matters and it's still peaking @ 2.2bar so all good..

 

as chip said its due to the gearing of the rollers. if theres less resistance it makes less boost. i had mine on a rolling road a couple of years ago, it was set up to 1.5bar with my own guage on the rolling road. out on the real road it did more than 2bar.

when it was mapped last summer on a brand new RR it did the same boost on the road.

 

as said above ramp rates and a good operator are needed......mine has never made "full" boost one the rollers and is always loads of rpm out on the graph aswell.....the last r/r i did was the closest to my on road boost, (i always sit in the car and look at my gauge)

 

STEVE SEE MY POST ON THE T34 400BHP THREAD LOL BEEN AN EVENT FUL DAY

 

Some interesting replies and good to know too, i was getting paranoid...Lol..

 

Just read it, great news Mark finding your problem.

Sounds like you had a little off in the car

Steve

 

yep had a run in with a bmw lol but its not that bad but im just gunna replace the panels and make it mint so 2k for bodywork on the cards