Hi Guys,
I've been debating fitting an uprated intercooler to my MY98 UK car for some time now and would like some opinions from owners who have fitted them. I know people say that a front mounted intercooler will result in a loss of response and an increase in lag but has anyone here actually run with one and what were your views. Also top mount intercoolers, has anyone upgraded to a bpm or mrt and if so what were your views??

TIA,
Nito

 

Hi,

I have a HKS front mounted intercooler. It is for a later model amd mine is a MY94 so was a bit trickey to fit. It has quite alot of pipe work so would normaly suffer fron alot of lag, however I also had a better roller bearing turbo fitted and that has made up for alot of it. You can still feel it a bit but it is quite easy to live with...

Spence.

 

A couple of links to look at:

 

BTW, why is this in "Suspension" ?

Thanks

Gavin

 

Gavin

Is XMS Australian for BPM? Seems to be the same old kit.

Moray

 

Moray,

I think they are a reseller - I was looking for the bookmark to the "Dual Entry" intercooler page and clicked on the wrong one

I added it to my post anyway as it was additional information - but you are quite right, you could approach BPM directly I'm sure....

 

Have you considered fitting the front mounted intercooler, and then removing the dump valve?

The theory is that this can actually <i>reduce</i> turbo lag, and may offset the losses from fitting the front-intercooler. May cause the turbo & pipework to be put under a little more strain though.

Andrew

 

Another idea (advocated by Australian tuning company whose scoob is featured in 'Banzai'magazine) is to fit two dump-valves; one near to the throttle body and the other near the turbo thereby releasing more air and keeping the turbo spinning more effectively and compensating for the pressure-loss generally associated with large Front-mounted intercoolers.

 

I read that Banzai article today and was rather intrigued. Nice engine, shame about the rest of the car .. just not to my taste I guess!

The theory behind removing the dump valve is this ...

Imagine the pipework & intercooler volume between the turbo as a big balloon. This gets filled up with pressurised air when the turbo's spinning. When you snap the throttle shut (i.e. during a gear-change), the dump valve allows all of this air to escape, meaning that the turbo has to effectively inflate this balloon again.

The more pipework & intercooler volume between the turbo and the throttle (i.e. with a front mount, larger intercooler), the greater the balloon effect. I.e. you've got more volume to pressurise before maximum boost is attained. This is why big front-mounted intercoolers cause more lag, and worsen throttle response.

When the dump valve is taken out of the equation, you get the problem of the pressurised air pushing backwards through the turbo, putting strain on it and causing it to stall. But ... at the same time, the pipework retains a much greater amount of its pressure between gears, meaning that the turbo has less work to do to get back up to full boost when the throttle is re-applied.

With increasing intercooler volume the benefit of a dump valve decreases, and the gains from removing it increase. (Or so my theory says!)

I know of two people who have recently removed their dump valves. One from a UK spec Scooby (at the recommendation of a well-known tuner), and another from a 350 bhp 4x4 Cosworth. Both have reported a *decrease* in lag between gear changes, and an improvement in throttle response.

I'm by no means an expert though! And I wouldn't want to take any responsibilty for any turbo damage that may occur. Please consult an expert before attacking your dump-valve!!!

Andrew

(I await your superior knowledge guys!)

 

Removing the dump valve definately improves pickup and response during gear changes but does shock the turbo as the impeller has to fight the sudden stopping of the air flow when the throttle is closed. A good compromise is to increase the pressure at which the bov opens and so you get a lessening of the shock at high pressure and still get improved pickup due to some retention of lower pressure. My car is an early one .. the bov cracks open at a lowly 2/3 psi, I modified it by shimming the spring to crack at 8 psi, now I have the best of both worlds, much crisper pickup. A good aftermarket recirc bov (such as Forge) will have a much stronger spring and achieve the same effect.

Bob

 

Interesting suggestion Bob.

I took my the dump valve off my MY97 Turbo this morning, partly out of curiousity, and partly to see how easy it would be to shim the spring to see if I could increse the activation pressure.

It appears to be a sealed unit, and I don't really want to pull it apart in case I damage it beyond repair! So I think that's a no-go.

Whilst I had it off (pardon the expression) I plugged the three pipes that lead to it and to my dump-valve-less car out for an exploratory spin. As you said, the between gear pick-up is almost lag-free, feels fantastic. Much nicer! I also get a lovely and extremely loud flutter (sounds like a full-on rally Cossie ... urgh!) as the boost rushes backwards past the turbo impeller.

Having said that, I don't want to put any extra strain on the Turbo, so as soon as it stops raining, the standard valve is going back on.



A.

 

Hi Andy

Mine made the same fluttering sound.Its a shame it doesn't do it all the time cause it sounds really cool !!

Oh and back to the original topic,Nito I have been wondering why you want to change the original,is it causing you problems or do you just like the idea of a FMI.

Andy

[This message has been edited by AndyMc (edited 27-05-2000).]