I'll post this here as it's no doubt of interest to others and I'm hoping someone on here can answer the questions.

Ages ago I bought a Mitsubishi Pajero intercooler and pipework having been told it was OK for my M45 supercharger installation on the 1.6 MX5 engine which is currently running without intercooling.
Currently it's producing c.199FWP but I'm aiming for 225FWP having also sourced larger injectors and an induction kit.
Now in the process of fitting it and doing a bit of research I'm wondering if its the right size.
General consensus seems to be the I/c needs to be optimum size - too small and it will constrict the charge, too big and pressure will drop.

So the questions are:-
1) Is the Pajero i/c suitable for that sort of power?
Body size is 350mm wide x 195 high x 60 deep.
Also the inlet/outlet pipes are 47mm diam v. 55mm on the AFM outlet.
2) Will stepping down from 55 to 47mm cause any problems?
3) Is there a link whereby I can calculate optimum size without needing a Degree in Maths?
4) If not suitable can you recommend me a suitably sized I/c?

TIA, Pewe

quote:

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Originally posted by pewe
General consensus seems to be the I/c needs to be optimum size - too small and it will constrict the charge, too big and pressure will drop.

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What about throttle response vs size of intercooler? Or is that related to pressure as well?

A huge intercooler with drainpioe diameter pipework and a T2 turbo running at 7psi and yes response is affected
But so long as the turbos running at a reasonable pressure and is close to the right size for the purpose then its not a major issue.
Keep the packaging in mind though, again pointless huge diameter pipework if its a responsive a sensibly sized turbo. Better to have all tge componentry at 85% ideal than the perfect IC and crap turbo, pipework and location.
Shield from radiated heat and ensure (just like a water rad) you have a good sealed entry duct to the ic core and same on exit. Scoop or bumper duct opening is ideally about 65% of core area, that way the airflow speed drops, the air cools more efficiently as it slows over the core, and then reverse for the exit, retun to 65-70% exit size. This speeds up the aorflow so when it exits over the bonnet or under the car its back up to road speed, albeit warmer! And doesnt give turbulent flow. Less of an issue on a 7 as it has barn door drag figures but every little helps :-)
Bar and plate ICs are nice if you are looking at running 15-20psi, also bit more resilient to damage from stones etc if you have a trip to the scenery...OEM ic cores are much lighter though and often nice and compact and efficient at their designed flow rate and boost pressure range

Yep, just to add to the numbers here, it's better to have a slightly oversized ic than undersized. The lag you get from a 25% oversized core would be in the millisecond range - at 200HP you're using around 140 litres of air per second - a 200ml increase in ic volume is a drop in the ocean of airflow even when considered as a transient.

Sure you want to minimise pressure drop though, for every psi you drop over the ic, the turbo has to compress first meaning longer times to boost, more heat generated and then needing to be removed.

Sure if you're fine tuning you can improve slightly by matching parameters perfectly but oversizing is definitely better than the opposite.

Thanks for the replies - lots of food for thought.
I came across this one but TBH it's about as clear as mud - can anyone offer a simpler explanation or am I just being a maths dummy?
Cheers, Pewe10

Not got time to look through the maths and check it's right, but assuming it is it should be fairly straight forward to plumb numbers in. That said - it's more down to what's available and what numbers you have and you won't have any decent numbers on things like heat transfer coefficients of your IC so it's all going to be based on estimations. If you want to do it right you'd datalog pressure and temperature pre and post IC and at a couple of other locations and identify where you pressure and temp drops are and to what level. That would help you tune the system from the theoretical values.

If it looks about right......it's probably about right

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Originally posted by dave_424
If it looks about right......it's probably about right

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This guy is running 1300WHP through large eBay/china intercoolers. Don't be fooled into thinking a name brand intercooler will perform wildly better than a cheap one. It's just a heat exchanger at the end of the day!

https://www.youtube.com/watch?v=TF5noFTpO-8

[Edited on 18/7/16 by dave_424]

Yeah I think the last couple of posts sum it up really - don't be suckered into thinking something will be a perfect solution because of the name or someone saying it's perfect, and don't expect something that seems wildly wrong to be right. Engineering judgement works well in a lot of cases - match diameters as closely as possible, keep bends to a minimum, get the biggest IC you can fit within reason without compromising other things. 55 down to 47mm seems a bit of a step to me but it would worry me only after I'd datalogged it and proved it was a problem - until then I'd just keep it on a list of things to improve with time.

I'm comfortably running 300hp through a 250x300x50mm core - it gets a bit toasty after a lot of driving but it functions fine 90% of the time. If I were tracking it I'd go bigger but for road use I rarely get to push enough heat into it to see exit temps over 40C at 15psi ~7000rpm. Again though this will depend on your super/turbo sizing too - a super/turbo running out of it's optimum efficiency will/may require more cooling to get the same pressure, so you'll need a bigger IC. What sort of boost are you planning to run? The pressure/temp ccurves for eaton chargers are available online for a starting point and some imagineering.

[Edited on 18/7/16 by coyoteboy]

[Edited on 18/7/16 by coyoteboy]