Suppose that while wheeling a rock came up and punctured the intercooler, or whatever. what would the risk to the engine be if the intercooler was bypassed for a long period of time. I know towing is probably out and power will take a hit too, but is there risk of damaging the engine with just normal driving?

I don't think you would get far, it would go in limp mode. Best to do tempory repair.

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The intercooler cools the compressed air coming out of the turbocharger. Bypassing it will a significant negative impact on power, increase your exhaust gas temp, and increase your fuel consumption. I do not know if the computer would detect the loss of the intercooler directly, or because other temperatures or fuel flow was out of whack.

Repair it - and get some armor to protect it.

As long as you don't hot rod it it would be fine. The only way the computer could tell anything is if IAT got to high, which it won't if you take it easy.

greg

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Greg
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2nd.

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Based on Air Input Temperature readings with and without the ORM, if you did the ORM, bypassed the CAC and drove easy, the AIT might not be much higher than normal without the ORM. Your could certainly stop once in a while and feel the hose (carefully) to see if it's getting way too hot or just read AIT with a scan tool while your are driving. The CRD has probably single-handedly driven up the stock price of companies that sell scan tools.

well I made the bypass pipe today. got it installed and test drove it. it rode pretty good, nice power definitely (not more power just not too big of a reduction) sounds more more like a normal engine too, the intercooler really chokes down the intake noise.

my main concern is the the intake temps read up to 265F out of the turbo @ full-go (I installed a thermocouple) and that's pretty hot i guess. it runs at 160-170F @ 65MPH cruise. does anyone with a scan-gauge know what the inlet air get up to as read from the IAT sensor?

I think I will drive to work tomorrow (33miles one way) and see what MPG I get to see if its worth investigating more.

I seem to recall 140-150 range on the scan gauge. ORM dropped the temp to about 10 degrees over ambient temp. It is shocking how hot the EGR got the intake air.

The intercooler does an important job. I wouldn't bypass it any longer than needed or run the engine hard without it.

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thanks for the reply, if you have seen 150, then 170 is not out-of-line for warm cruise.

I have read that when a CAC gets coated with oil on the inside that its efficiency goes way down, and my truck passes enough oil to foul the CAC despite the EHM. also the truck only sees 5-7 PSI continuous for warm cruise (65MPH). based on those conditions a CAC is not really required except for burst power, towing or other continuous duty above 6-8 PSI boost. the big idea I want to try, is to have a low restriction intake pipe (less distance really, the stock intake system is pretty darn good) and then use water/meth injection for cooling during burst power. for the small amount of towing I do, I would reconnect the CAC. for the most part I drive on flat oh/mi highways at 55-70MPG for hours on end and want to get 550-600 miles per tank. I get 510-540 miels per tank now.

on my 66mile round trip, plus ten miles of testing yesterday I am averaging 2 EVIC MPG higher than before. This will prompt me to let it go for this tank and see what real MPG improvement I can see. it might be slightly biased since I am not getting on it all (no intercooling afterall) but I did look at some nice alky/H20 injection systems and will pick up a good one as soon as possible to alleviate the issue.

this one shows the placement of the thermocouple, just under the AC hose.





I have a 300+ mile road trip planned next weekend and will reactivate the CAC to do a mileage check after as well.

The increase in MPG may just be because you are ingesting less oxygen into the engine.

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I recorded 27.46 MPG hand calculated which relates to about 550 miles per tank, which is not bad. I normally run 25-26.5 MPG overall. My EVIC sure does read a lot higher than that though. It showed as high as a 33.5 during this tank, and it usually is between 2-4 MPG off (always on the high side) but I have not seen 6+ MPG off till now, it’s basically useless being this inaccurate.

I think there is promise in bypassing the intercooler for some portions of the drive cycle. Even the best CAC has a 1 PSI pressure drop, so getting rid of that cause the compressor to make 1 less PSI and thus the turbine to require 1-2 PSI less backpressure to make. Perhaps a bypass valve like from an OEM turbo car can be used to circumvent the CAC during cursing, but close at full power to force the air through the CAC.

Here's a couple of things that I'm worried about in bypassing the CAC:

1. The maximum allowable temperature rise between the ambient and the intake air temp (after CAC temp) is 30 degC during continuous duty use. Given an 80degF day (26.6degC), that means you can't have anything over 110 degC in the intake. However, with the CAC, your normal IAT is going to be more or less ambient given sufficient air flow thru the grille. The temps coming out of the turbo compressor are going to be well over this value, thus you're going to be in a position where the engine performance is being derated considerably. Plus these high temps - even during low load cruising - aren't going to be good for the combustion process.

2. The max allowable specs for delta_P across the CAC is 100 mbar and the DCX CAC meets these requirements. Thus your pressure drop is much less than the 1psi, and isn't really an issue. Addtionally, the back pressure increase from such a small movement in the turbo vanes is negligible in comparison to an appreciable drop in fuel economy.

The reason why your fuel economy went up is that the super high IAT's caused the EGR to shut off as well as ambient corrections for injection quantites and timing to come into play, thus making it run differently.

1. I mostly agree, and the ambient + 30degC IAT maximum seems very reasonable too. that would make the maximum IAT ~140-150F and I was around that without the intercooler at 55MPH. but I don't see how hotter IAT is going to be bad for the combustion process (maybe for power but the diesel combustion?), can you explain why you say this?

2. 100 millibar is 1.5 PSI, by my math. i would be very surprised if the CRD had less than a 2:1 back pressure to boost ratio, (do you have any data on this?) delta 2 PSI of back pressure seems like alot to me.