boost @ topspeed

[$ven]

Hello people,

Just thinking of this; there has been a lot to do about boost controllers on here lately, but one thing, isn't clear to me.

Let's take the Greddy profec-B for instance, everyone rates this boost-controller as being; user-friendly,easy to install, no special unneeded gadgets,etc... Just enter the boost you like and that's it.

Let's say we set the boost at 1.2 bar, does it run 1.2 bar all the way? Might be no problem for a slightly modified and healthy R, to run this 1.2, and to do some 1/4 miles and stuff. But if the boost is still 1.2 bar @ 220 km/h, I'm quite sure that this doesn't help keeping the engine healthy.

I know of the AVCR, having options to decrease boost in different gears&RPM, but how do the other boost-controllers solve this problem? (or do they really work like a good old fashion bleed-valve, and just keep it at 1.2bar?)

 

[Si..]

i've heard of prospeed's evo's having map's for 1.6 bar peak and tailing down to 1.4 at the top couple of thou in the rev range,

as for the boost controllers your on about i can only go off my pal's profec and yes that keeps the set boost level from full boost to the end of the gear. and i dont think it can be set up to do otherwise.

isnt that what you want tho :? ?

 

[Rishi]

If its good enough for the 1000bhp JUN Supra and Simon Norris' 800bhp EVO... Then its probably good enough for you...

 

[youngsyp]

The only adjustment you could make is with your right foot

As for trailing the boost pressure off at high rpm's, it would be beneficial for the longevity of the engine. At the top end is where the engine would produce the most heat and as we all know, the higher the boost, the higher the charge temperature. You can figure the rest out. Then you have the engine working at it's hardest and every component moving at it's fastest. You soon get the picture that the least stress you can put on at high rpm's the better.
Another point is that the harder the engine is working, the more gas it is expelling through the turbo so, the more charge is going into the engine. This will probably negate the need for such high boost pressures and be creating the same sort of power at a lower boost pressure.
I have to admit though, I have a AVCR and haven't got this deeply into setting it up yet but, do plan to do so !

 

[$ven]

If its good enough for the 1000bhp JUN Supra and Simon Norris' 800bhp EVO... Then its probably good enough for you...

I'm not saying that I think the Profec is a bad boostcontroller, but obviously this 1000bhp Supra and 800 bhp EVO are not daily driven, so there's not so much need to protect the engine at topspeed, since it's tuned for power only instead of reasonable reliability.

This will probably negate the need for such high boost pressures and be creating the same sort of power at a lower boost pressure.

That's what I mean. There really is no advantage of having the boost setting to be at maximum for topspeed. Ofcourse the right foot can control everything, but if possible, I'd rather not think about it, and use the AVCR options.

 

[Shaun]

$ven,i can see your point,but i thought this is where the dyno set up and fueling came into it Also if you look at alot of dyno print outs,the optimum power is below the rev limit and the power tails off anyway :!: Also,who runs their car at top speed everyday :?: Personally mines not been above 120mph since i've owned it :!: The only advantage i can see is to safe guard the engine if your either running mental boost pressures or standard internals :!:

 

[Anonymous]

If you experience boost drop at higher revs, then this is because the turbo can not supply enough air to maintain boost at high rpm. This is not a fault of the boost controller, just means you need a bigger compressor on your turbo.

On my MR2 for example, complete with 48 trim T-04E compressor I can hold 28psi to the 7800rpm rev limit. On the original turbo with it's crappy 30 trim compressor it would only manage 14psi at the original 7200rpm rev limit. However that turbo could make 20psi at 4000rpm. The boost drops because the smaller turbo simply couldn't move enough air in to the engine fast enough to maintain the set boost pressure, even with the wastegate jammed shut!

 

[Shaun]

Ben,you've missed $ven's point mate Read his post

 

[$ven]

Shaun thanks for reply,

if you look at alot of dyno print outs,the optimum power is below the rev limit and the power tails off anyway Also,who runs their car at top speed everyday Personally mines not been above 120mph since i've owned it

This is true, haven't thought of this before. About the topspeed, I don't do topspeed everyday either, but sometimes :twisted: :twisted: Ofcourse it's not a BMW 750, cruising 200 km/h all the way from Amsterdam to Vienna, but sometimes you just have to re-educate these people. 8)

Anyway, already have forged internals and Tomei headgasket, so you recon this shouldn't be a problem then @ 1.2 bar? (for initial & short use)

Ben, thanx for usefull info :lol:

 

[Shaun]

Hi $ven,glad i could help I'm running 1.18bar on standard internals producing 328bhp and the only thing suffering is the clutch :lol: As its the standard item :lol: 1.2bar seems to be the average boost pressure for a lot of people to run who want a little more power than 1bar,but not the expence of a re-build And as long as it's set up with the right fueling it is as safe as anything can be Also Duey is running 1.2bar with no problems what so ever (also on standard internals).So with your spec $ven,and the right tunning of course,i cant see you having problems :!: