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Author Topic: Too cool?  (Read 11196 times)

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Offline Blue

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Too cool?
« on: August 29, 2008, 11:21:38 PM »
A lot of the turbo'd entries seem to have truly awesome ice-bath intercoolers.  Has anyone had issues with fuel not vaporizing properly due to sub 50F inlet temps?

I saw many examples of uneven cylinder-to-cylinder fuel distribution in otherwise good setups.  It reminded me of my early schooling in wet manifold and heat riser theory.  No, the higher RPM will not solve this issue; it actually makes it more critical.  Has anyone done a plug chop run vs. run and seen unexplained variations?
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landracing

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Re: Too cool?
« Reply #1 on: August 30, 2008, 12:04:14 AM »
I would be suprised if anybody had 50 degree inlet temps. Lots of ice-baths but lots of boost and a 5 mile run. I dont think anybody has those types of temps coming into the 4-5 mile.... There are some that I know that have at close to ambient temp 90-100 degree temps.

Jon

Offline dieselgeek

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Re: Too cool?
« Reply #2 on: September 02, 2008, 08:55:33 AM »
our ice bath setup nets us about 105 degrees F at the end of a run, and a minimum of about 70 degrees F at the start.   But this is a good point, I had this issue in a drag car where we were able to soak the intake before a run, car would misfire a little, and saw uneven distribution on plugs, and this all occurred right around 50-55 degrees F intake temps.  (We're using GM IAT sensors, we calibrate them to the computer but they're not exactly laboratory instruments  :-) )

Offline Dean Los Angeles

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Re: Too cool?
« Reply #3 on: September 02, 2008, 11:43:45 AM »
Ice bath intercoolers don't have very much time to do their work. The contact time is pretty short. The only place too cool might come in to play would be starting a too cold engine.

I think there is lots of room for better cooling with dry ice/methanol or dry ice/calcium chloride brine.

Too cool? At some point the charge temperature will interfere with ignition. I doubt you can do that with ice.

From a BMEP standpoint you want the hottest vapor temperature possible. The reaction is faster with higher temperatures. Pre-ignition and detonation are limiting factors.

So why cool at all? To get more air in the cylinder. There is some crossover point where the air density and ability to ignite cross and horsepower suffers but I don't know of any research on that.

The fix for too cool air is heated fuel. Honda in the past heated the fuel in their F1 engine to 180 degrees F to maximize horsepower.
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Offline jl222

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Re: Too cool?
« Reply #4 on: September 05, 2008, 10:20:38 PM »
  I've tried for years to get blown alcohol and nitro temps from drag racers and others but incredibly nobody i've asked records them. It would seem  that blown alcohol would be a very low temp as they have no need for intercoolers.
 Airplanes must incounter very low temps at high alttitude.
 Honda turbo FI had a means to keep air temps near 100 degrees constant.
                                   
                                    JL222
 
 Anybody out there with alcohol or nitro temps?
« Last Edit: September 05, 2008, 10:28:26 PM by jl222 »

Offline Grant Borman

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Re: Too cool?
« Reply #5 on: September 05, 2008, 11:03:54 PM »
The fix for too cool air is heated fuel. Honda in the past heated the fuel in their F1 engine to 180 degrees F to maximize horsepower.

This may be in part to the large amount of toluline they used in their fuel which at higher mixtures has to be used at an elevated temperature or else it will not ignite easily.  Its all relative to the fuel used. 

Although I will say I have been wondering how fuel temperature relates to fuel economy.  If you heat up gasoline until its a vapor you would think the more homogeneous mixture would be better for fuel economy.

John Romero

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Re: Too cool?
« Reply #6 on: September 05, 2008, 11:27:38 PM »
I run a methanol fueled turbo 4 cylinder with no intercooler. I typically run an increasing boost level (versus speed) and max out at 23 PSI. I have 2 large injectors that deliver about 35% of the total fuel used near the turbo compressor outlet. The injectors are facing rearward (face first into the flow, not with it).

On a 71 Deg morning at Bonneville my minimum intake temp was 64F and the max was 90F at the end of the run.

I run EGT's and AFR sensors in each hole for testing and found no serious cylinder to cylinder variations with the differing amount of fuel delivered at the turbo.

On a different note, I used to work on methanol turbo champ car engines in the 90's where we developed basically the same thing. The basic rule of thumb we finally settled on regarding how cold you can take an intake charge before you simply have raw fuel flying around like a washing machine is the local dew point temperature.

Since the Indy motors did not allow variable intake trumpet lengths, we varied the target air temp based on engine RPM to dynamically move the peak power RPM via fuel delivery to get the same result. Pretty much any reasonable intake air temp from about 50F to 200F could be achieved by simply increasing or reducing the amount of fuel delivered at the turbo inlet (1994-1996) or the compressor outlet (1997-2001). Again, the lower temp target limit was set to the local dew point.

Also, too much fuel had a tendency to explode the plenums. Allot.

Offline JimL

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Re: Too cool?
« Reply #7 on: September 08, 2008, 09:54:08 PM »
I had difficulty with the gasoline-turbo application.  Spark plug porcelin clean white, exhaust sooty black, cylinders washing, acted like it was lean and wouldn't spool the turbo, wouldn't rev up....you name it.  Black soot the whole length of the exhaust side of the body!  This happened with the stock (small) intercooler and with the huge unit we added in 2000.

I went back to the fuel truck and got the lowest "90 degree distillation temp" gas they offered (ignoring the octane numbers and the offered advice, etc.).  The car went from 101 mph to 183 mph on the next pass, with NO other changes.  It was running on a stock Toyota All-Trac Turbo ECU, without feedback control.

Seen that "heavy fuel" issue take down a number of folks, with and without turbos.

Just my 2 cents.

Regards, JimL

roadtrip

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Re: Too cool?
« Reply #8 on: September 08, 2008, 10:09:06 PM »
25-30 years ago Smokey Unick was doing research with super-heated (vaporized) fuel (gasoline) at the carb.

Shouldn't be hard to find information on that subject.

Offline javajoe79

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Re: Too cool?
« Reply #9 on: October 15, 2008, 11:06:25 AM »
The hot vapor engine. He talks alot about it in his biography. Seems like it would be fun to try and build one. His was turbocharged. The fuel air charge would get blown through a radiator built off of the exhaust. It would vaporize the fuel just before the engine sucked it in. He was able to make great power with very little fuel.
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Offline jl222

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Re: Too cool?
« Reply #10 on: October 16, 2008, 01:58:57 AM »
 I remember reading about that engine [long time ago] seems it was a v six cut in half no radiator and heated the fuel somehow before entering the turbo which he said homoginized the mixture but the tubo was not used for boost somehow,but the engine did get boosted from the heated fuel mixture.Pretty vague on stuff but seems he
drove car to Washington D.C. and got like 60 mpg.

                           JL222

Offline javajoe79

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Re: Too cool?
« Reply #11 on: October 16, 2008, 10:04:09 AM »
 Yeah he talks about the fuel mileage challenge amongst the big three. I think the car was a pontiac with an Iron duke. He said they would drive on sidewalks and through ditches, to coast around standing traffic, so they didn't stop and hurt their mileage.

  To anyone who hasn't read Smokey's book Best Dodge Garage in Town, you should go buy it now.
I need to get mine back from my friend Louie, I want to read it again.
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Offline Dean Los Angeles

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Re: Too cool?
« Reply #12 on: October 16, 2008, 10:47:40 AM »
Quote
Smokey's book Best blue jay Garage in Town

Ah, the filter.

Smokey's book Best D-a-m-n Garage in Town,

Well, it used to be Los Angeles . . . 50 miles north of Fresno now.
Just remember . . . It isn't life or death.
It's bigger than life or death! It's RACING.

Offline fredvance

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Re: Too cool?
« Reply #13 on: October 16, 2008, 11:13:09 AM »
I was wondering what the H-e-l-l a blue jay garage was. :-o
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Offline Stan Back

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Re: Too cool?
« Reply #14 on: October 16, 2008, 11:26:43 AM »
I think it was a truckstop last month.
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