Outer Limits 4x4 Board

is an air to water intercooler the best for offroad or is a top mount with a thermo fan cheers

Best depends on the judgement criteria - Best heat exchanging performance oir best reliablity or best trade off for both?

I should say firstly that I havent done a air/air top mount but UGOTNUFN has a huge one on his GU TD42Ti and apparantly his intake temps are sub 70deg C worst case.

From a simplicity and trade off perspective, I would go the top mount air/air.

For outright performance, I would go a simple 4 core laminova or even one of those 11"x11"x4" water to air cores off eBay. In both cases, the key is attention paid to coolant flow rates and a decent at least 600*300mm core at front for heat exchanger.

I recently decided to put a front mount air/air on my 1HD-FTE (I have it, but not installed) and I seriously considered the options to the point my finger was on the buy (I actually do have one of those 11" water to air cores I mentioned - will happily sell it now as I dont need it). Mine is auto, so delay in filling the larger volume is not an issue as much as it can be in a manual.

I have run w2a and a2a on my 4.2 GU and for a diesel would go top mount every time for a 4WD. It is simple, lag is minimal and when you really need it at full boost your normally moving at a speed fast enough that it is working.

I had a PWR w2a (10x6") and the unit did work, no question about that but it is more complex and with that comes costs. You also need a much larger front cooler than what PWR gives you and it gets clogged with mud, bugs and other things so you need to keep checking that it is clean (same reason against a front mount a2a cooler).

Top mount is just the perfect compromise for my use and I wish I had done it in the first place and not wasted all the money on the a2w. Though no question the a2w setup can potentially be much more efficient and provide more cooling, it comes at a cost & complexity that is not required from all but the wildest 4wd engines.

- David.

well cheers for the input i reckon i will be making it a top mount