Thread: Biggest Intercooler for Isuzu 4BD1T

I don't think that there IS a theoretical limit. The lag problem seems to be a bit of a furphy to me - the speed with which an increase in pressure (as the turbo speeds up) through the entire intake system is going to be the speed of sound - so the only effect will be the need to fill a larger volume, which I suspect will be marginal.

On the positive side, the cooler the better no matter how you look at it, and the larger the intercooler the smaller the flow resistance will be. In both cases it will be a case of diminishing returns, but I think that the practical limit (what will fit) will be reached long before the improvement of going bigger is negligible. So what they told you is correct. I doubt that there is any sort of formula, and if there is it will be a rule of thumb, and probably directed at the smallest one worth fitting rather than the largest.

John

rijidij

Mate, I'd be interested in what people have to say on this as I've been looking for an answer to this exact question over the last couple of days.

After a bit of searching I came to the conclusion that you wouldn't put an intercooler in that flows excessivly more than the flow capability of your turbo can supply. I know that the Garrett website has the flow spec's for their turbos, then it's just a matter of getting a intercooler that can match it. I probably wouldn't get one that is too big as I don't particularly want to spend any more money than I need to.
I do think John is in the ball park though, I mean once there is 15psi in the system there is 15 psi in the system. If there was a noticable amount of lag when you put your foot down then there would be a pressure dop at you boost gauge. I don't notice this happening.

One thing I have noticed while trawling through the web for intercoolers is that, even though I'm a big preecher of e-bay buyer beware, I'm struggling to spot the differance between the $900 intercoolers that are advertised in the shops and the 150$ ones of e-bay. Anyone with personal expearience out there please add your thoughts.

Also, where can you buy cores from, I wouldn't mind making my own header tanks an doing one up myself. They use to sell on e-bay cheap, I figured if they were crap cores then I wouldn't have lost much in the sceam of things

Cheers

Originally Posted by JDNSW

, but I think that the practical limit (what will fit) will be reached long before the improvement of going bigger is negligible.

John

Thanks JD,
This is what I was thinking too. In the case of a County where you want a front mounted air/air IC, you are limited to what will fit between the guards length wise, and between the radiator and the plastic grill depth wise. In my case I have the A/C grill with the condenser removed, so I have a bit of space to fill if I so desire. I don't think filling this available space with intercooler would be 'too much' for the 3.9.

But hypothetically (and grosely exagerating), if you fitted an IC from say, a 16 litre V8 diesel truck engine to a 3.9 litre engine, this would be way too big and would have to have a negative effect on performance. I'm guessing this IC would be something like 9000 cu/in (they are huge)
So, somewhere between say, 800 to 9000 cu/in is the biggest size IC that the 3.9 engine would benefit from.

Just curious, that's all.

Cheers, Murray

Originally Posted by Larns

After a bit of searching I came to the conclusion that you wouldn't put an intercooler in that flows excessivly more than the flow capability of your turbo can supply. I know that the Garrett website has the flow spec's for their turbos, then it's just a matter of getting a intercooler that can match it.
Yeah, that's what I mean by some kind of 'formular' to work out the appropriate size for a particular engine/turbo.

One thing I have noticed while trawling through the web for intercoolers is that, even though I'm a big preecher of e-bay buyer beware, I'm struggling to spot the differance between the $900 intercoolers that are advertised in the shops and the 150$ ones of e-bay. Anyone with personal expearience out there please add your thoughts.
I bought my brand new intercooler off EbayAU. $89. I was a bit sceptical until it arrived in the post. As it turned out, it was made in the States, seemed very well made, was the newer bar and plate type, and I was very happy with my purchase for that price (I think I was lucky). This is the exact type that I got >>>>>>>>>>>

cxracing.com: Front Mount Intercooler 28"x7"x2.5", 2.5" Core: 22"x7"x2.5", 2.5" Inlet & Outlet, , BMW Audi A4 Golf

Cheers, Murray

I had problems with an oversized intercooler on a De Tomasu and then the same problem on a Bi Turbo years ago, but that was due to the fact of it acting like a big pressure reservoir against a closed butterfly at low rev's . But none of that relates to diesels so i would say bigger the better ( but not a truck one)

some great articles on autospeed about sizing intercoolers among many more:
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Corky Bell has abook on turbocharging engines, it is about petrol engines but some things still apply. lets see what I remember without having to pull the book out.

Volume in not necessarily the best thing by which to compare i/c. Area provides better returns than volume. The thick i/c does not provide the same cooling to the back part as it does to the front as the air passing through has already picked up heat from the front. In terms of area more air passages are better that long air passages.

I do not understand the reference to the speed of sound. I think the time it takes to get a volume up to pressure will depend on the volume rate that the turbo can push air into the i/c and hoses. I don't recall the detail, it could be something inperceptible for all I remember.

From all that I would say go for more area not volume, go for wide and short not long and skinny.

Originally Posted by rijidij

Cheers, Murray

Hi Murray, FWIW my I/C is the same as yours, except about 1/3rd taller. Mine was branded 'Hybrid', and was supplied through an aftermarket accessory supplier.

JC