Inliners International Forums General Discussion Engines Draw Through vs Blow Thru Turbo

Well, with all the talk of turbocharging lately and the many discussions of whether or not to use blow thru or draw thru...lol Id like to say ive had a revelation. ive always been a proponent for blow thru for the main reason of being able to use a intercooler to achieve more boost. now draw thru especially for our I6's would be the easier of the two to try, but as everyone knows, and intercooler isnt the best idea due to possible explosion that would occur if a backfire ignited the fuel puddling in the intercooler.
well my revelation, and im sure im not the first to think of this, is in the form of an intercooler for a draw through system. in the two feet or less of intake pipe going from the turbo to the intake manifold, why not form another pipe to fit over the intake pipe, block off the ends and run coolant through it. you could use a separate electric pump and a aluminum tranny cooler to achieve a cooling affect around the intake pipe.
this might not be as efficient as an air to air intercooler, but even if this design is 30% efficient it would allow for much higher boost and power.
sorry for the long post but what do u think?

I didn't quite get what you said..

For a second I thought you wer talking about putting the intercooler before the turbo.. That wouldn't make any sense because the air get hot while it passes through the turbo..

If your talking about having a small liquid to air heat exchanger in between the turbo and the engine, well this stup is called a liquid to air heat intercooler setup. They already exist. In my opinion they are too complicated.. But if I'm not mistaken they do cool the air more than an air to air intercooler.

Anyways, the problem from the draw through system would still be there though; the fuel will condense in the cooling stage and you don't want that. You want the fuel to go to the engine, not condense on the walls of the intake.

The only way that I can think of effectively cooling with a draw through setup would be with water injection, but I bet as soon as I post this about 2o people are gonna start posting on why you shouldn't take this approach...

Anyways that is what I know,
Luis

i actually thought about the effect of puddling as well, but there a a couple of things as to why i dont think it will be an issue;
1. Unlike a typical air to air intercooler the air/fuel mixture will not be passed through mulitple tubes just the intake tube whick never changes diameter so the sharp angles where fuel would collect should be at a minimum
2. another factor i believe will help minimize fuel puddling is the length of the intake tube itself, it will only be 2 feet max, vs the 6 or so feet required for plumbing with a regular intercooler
3. this isnt a typical water-to-air intercooler so the basic design is not complicated at all and should cost very much to fabricate
of course its all hypothetical at this stage so who knows but those are my hypotheses based on the research ive done. once i come back from deployment ill be able to start putting all this to the test.

yes I see now that your talking about a simple concentric tube heat exchanger..

I don't know what to say, I very well could work (I do not know enough to make a much more specific conclusion)

BUT, concentric tube heat exchanger aren't very efficient. You'll also want to have it be counterflow, (have the air and the water enter on opposite sides) to have better performance. If you are going to have the cold water on the outer tube you'll have to insulate it from the engine heat otherwise it will absorb the engine heat rather than the intake air's heat.

Anyways, the problem of condensation will not be as bad as with a regular air to air intercooler but I think there will still be a problem. For example engines that have carbs without heated plenums don't run too well.. see were I'm going with this..

Anyways like a said before, I am not knowledgeable enough about this to acurately guess whether it will work or not.

If you have the facilities, try it, tell us what you think and sell them and become rich!

I don't know nuthin,
Luis

I'm not expert myself. But I do know that heat exchange is dependent (all other things equal) on the surface area being considered. Double the surface area, ~double the transfer. That's why rad coolers,oil coolers, tranny coolers and intercoolers all have a large number of tubes, plus internal baffeling plus additional fins to add area.

If you're cooling just a section of tube you probably haven't got enough surface area to effectively exchange the heat from a turbo at full blast.

If I had to bet I would say that the goals for good ducting of air fuel mixes and that for intercooling basically don't mix.

But don't take my word for it. Just one man

what you say is very true, and after mcoking up where the turbo would go, i would require less than a foot of tubing for the intake, so i really wouldnt have any surface area to work with.
but ill try anyway for fun. i know there wont be a noticible temp drop at low boost but at higher boost when that intake temp shoots up, im sure ill see some drop in temperature.
also, how do you think some kind of a heat sink would do...links fins welded onto the intake pipe. or would that do no good since it would only be radiating into an already heated engine compartment?

With fins:

If you eliminate the heat exchanger alltogether then fins will improve heat transfer IN THE DIRECTION OF HIGHER TEMP TO LOWER TEMP. I don't know the temperature of an engine bay nor the temp of the heated intake charge from the turbo so I can't really say..

anyways, another thing you could try is having a multiple tubes with water flowing through them inside the intake tube. That'll get you more surface area..

Sorry for insisting so much but I still think that cooling air with the fuel already mixed in is not such a good idea.. I would seriously look into water injection. I started looking at info about it and was seriously surprised. And it seems to me that it is way easier to setup than any intercooler setup. In my opinion the only drawback to water injection is that you seriously have to check the water level..
Again, sorry for being so insistive..

Luis

Have you consider using EFI port injection, it solves a lot of problems with fuel drop out and what to do with the compressed A/F mixture if you are using a blow off valve to avoid shocking the compressor when you jump off the throttle.

as far as water injection goes, i had already planned on using it, the whole intercooler thing was just an idea.
with efi...i would love to use efi, but i really dont have the money. im trying to do an very low budget buildup and if i want to use my money to have good engine internals and quality turbo components efi just isnt in the question at this point.
with the blow off valve venting air and fuel, thats easy... im going to vent it back into the intake of the compressor.