Head temp differences, How big is too big? Options

[lapuwali]

I recently fit a CHT gauge, and originally put the sender under the #4 plug. Readings were in line with what I've read here: idled at 300dF, cruised at 325-350dF, touched 400dF under heavy load (lots of long uphill grades here).

I moved the sender to the #1 plug yesterday, and the temps are as much as 50dF lower across the board. Idles at 250dF, cruise about 300dF, never exceeds 350dF even pulling up a long hill.

I expected a difference, but not 50dF (20%!) between heads. I'm running Webers, so it's possible I have completely different mixtures for each cylinder. I presume cooler head temps would usually mean richer? This would be in line with plug colors (blacker on the 1/2 head, tanner on the 3/4 head). Hmmm....

[Jake Raby]

Absolutely...

50 degrees from the 1-2 bank to the 3-4 bank is typical....

The stock system is not a "DTM"!!

My fiberglass guy is making us a mold for a better stock blower housing..... It will have adjustable vanes inside it..

[mightyohm]

Not long ago I installed cooling flaps on my 1.7. Not knowing how they were supposed to fit I first put them in WRONG so that the right side flap was blocking all the air to that side of the engine. I drove around town for 30 minutes and noticed the car was running real rough at idle. When I got home I could FEEL the temperature difference across the engine!

PS. The engine still runs today.. and yes I am an idiot.
(IMG:style_emoticons/default/aktion035.gif)

[dmenche914]

I'll be getting head temp senders on mine, all four of them, still need to get the engine in the car, but I am cripples right now, maybe in a few weeks.

Temp seem to be typical from what i have seen on Bug motors.

Question: How did you install the sender, did you remove any aluminum around the spark plug hole to allow space for the sender? i did on mine.

Also: Jake, is this new fan shroud design for a stock installation (will it fit with 2 liter factory FI)???

And how bad is the type IV stock system, how uneven is the cooling?????

dave

[Jake Raby]

The replacement shroud is a 100% knockoff of a stocker on the outside, BUT inside is different....

Its my newest cooling challenge, and with my fan modification it is sure to be a huge improvement...

as far as differences from side to side:
anything more than 30 degrees is pretty radical, it makes the engine run at uneven rates, and screws up the efficiency.

[lapuwali]

Wait a minute. Is a 50dF difference "typical" or "radical". It can't be both!

[mightyohm]

It can be typical and still be bad for making power...
I think that is what Jake means.

[Jake Raby]

I'm saying that a 50 degre difference is typical with the stock system.... AND that its considered radical when compared to other engines because its more than 30 degrees..

The stock Type I is betterr than that, and so is the 356! The only thing worse is the VW Type III engine, they average 65-75 degrees hotter.

[tracks914]

50*F from front to back is OK (1-2 and 3-4)
But 30*F from side to side is not (1-3 and 2-4)
I think is what he means? (IMG:style_emoticons/default/blink.gif)
or not?

[Jake Raby]

Bank to bank... meaning:

cylinders 1-2 are a pair..
cylinders 3-4 are a pair.. I'm speaking of differences from bank to bank.

When you install a CHT on all 4 cylinders you'll see that both on the same side run within 5-10 degrees of each other and the rear cylinder is a tad hotter..

Even on a Harley this happens with the rear cylinder, its being cooled by preheated air from the forward cylinder.

I have been working on cooling system stuff for 2 solid years, and intensely for the last year... All I have really learned is until you have 9PSI, the air inside the plenums cannot be directed.. Thats the only general rule so far... everything is dependant upon something else!

[Dave_Darling]

So you're actually going to make another new cooling system that will fit the factory fuel injection? One that cools better than stock? That would be pretty sweet...

--DD

[Jake Raby]

Yes, the mold is being made now... It loks 100%factory but much cleaner. we pulled the outside of the mold from a cleaned up stock TIV shroud.

The inside will be fully adjustable on the test shroud..

I will perfect it after the 911 system. The Type I DTM is almost perfected, then comes the 911, and then the 914!

Wait till you see my method of creating more ashroud pressure, it'll blow ya away!

I'm totally involved in coolibng system stuff now, just bought a new 16 sensor data logger for the dyno, it reads in real time and downloads every 10 seconds into the P/C!

[dmenche914]

goodness sake jake (hey that rhymes) You are doing a great service to all us type I and IV Vw owners with you cooling work. I think we all will be owing you a big thanks for this work.

When do you expect the type I DTM to be ready, and what is the cost? Does it use stock fan and generator stand?

Will all these results be in the Ultra VW article?

dave

[Jake Raby]

ALL the cooling results from the TIV and TI test will be in Ultra VW in the next 6 months or so.....

The TI DTM is *almost* perfected, after a very simple change was thought about and put into effect the whole thing turned around..

The price will be 350-550.00 according to the actual cost of production when we get to that point. It does use all TI cooling parts, BUT it uses a TIV oil cooler in the stock TI oil cooler position. Thats one of the biggest benefits it has over anything else.... and it is a 1 piece design. Go to www.massivetype4.com for pics and some details.

[lapuwali]

There were several holes left in the tin from the carb conversion done by the PO, including the large one for the FI CHT (no present), and the one over the oil pressure switch. I taped up these holes and moved my CHT sender to the #3 plug, which Jake notes should run hotter than the #4, which was running at 300-350-400 (idle/cruise/load) over the course of several days. This morning, the temps were 280/330/380, so assuming outside temp differences aren't messing with things (I really need a dual gauge...), it looks like doing that cooled things down by 20-40dF, depending on how much hotter #3 had been running compared to #4 before.

Not all that scientific, but at least I did appear to reduce the temps a bit.

[dmenche914]

yes, all the correct seals on the holes are important to prevent loss of cooling air, and seals in the engine bay (big seal around engine, the two covers over the alternator adjustment holes) prevent heated air from getting in to the fan.

(i dropped 50F just by adding a fire wall in a type I powered kit car)

Beware of tapes to seal holes, many tapes do not last long in the engine bay enviroment (even duct tape) and when they come loose, they often get sucked into the fan, and get trapped on the cylinder fins, hurting cooling)