Thanks Don! We are looking for a certain HP goal. If we make that goal we will not lean on it much passed that...
Forced Induction's FI91X report!
- Thread starter Alky V6
- Start date
Thanks Don! We are looking for a certain HP goal. If we make that goal we will not lean on it much passed that...
I was checking over a book I have on racing with methanol and no where in the book is there a reference to avoiding an intake charge that is too cold. Actually, there is plenty of references to intercooling and none of it argues against using an intercooler with methanol. If the engine is under ported, which is not too hard with a 2 valve engine on alcohol, it is preferred to get the intake charge as cold as possible to provide a denser mixture and maximize cylinder filling.
Where did the idea that running too cold an intake charge is not a good thing?
And let's not forget that in most of the pro class racing supercharged intercooling is not allowed.
Where did the idea that running too cold an intake charge is not a good thing?
And let's not forget that in most of the pro class racing supercharged intercooling is not allowed.
- Joined
- May 27, 2001
Don,
Let me see if I can find my source.
I think it was an outlaw or promod site.
Or it could just be old age...
Maybe there was not a point where it was detrimental,
it may have been a point of diminished returns.
Today I modified the filter duct at the turbo. During inspection of the car after the weekend, I found the ducting unseated from where I had installed it. I had a few nasty backfires over the weekend tuning sessions and I think one of them must have been enough to try to blow off the ducting. To get the duct to grip the turbo better I hammer formed a 1/8" lip all the way around the turbo end of the duct. The lip acts to keep the clamp in place and not let it slip off the end of the duct. I also cut four slits in the flange of the duct that slips over the turbo. When the clamp is tightened the duct flange collapes further due to the slits and grips the turbo opening better. The lip prevents the clamp from sliding off the end of the flange. I also machined out a support bar for the up pipe to throttle body. I felt uncomfortable letting the wiggins clamp do all the work of holding that up pipe to the throttle body. The support bar now takes all the load off the wiggins clamp.
- Joined
- May 28, 2001
Pardon me for playing devils advocate but with the specific gravity of methanol and the amount you are throwing at it, could the intercooler be chilling the meth to the point where it is not atomizing very well through the intake? Maybe its not an issue with a turbo stuffing the manifold.
But a shot of nitrous combined with methanol has to be cooling off things pretty well. Just thinking out loud here.
Which brings us back to the main question. How cold is too cold with methanol?
Let's take a look at an alcohol injected, naturally aspirated engine. How cold is the intake charge in that application? Air entering the engine is at atmospheric pressure. The temperature is ambient. Compression ratios of 16+:1 are used to heat the charge for proper vaporization during compression and combustion. I've never heard of anyone saying that ambient intake air temperature was too cold for a naturally aspirated, alcohol injected engine.
Now let's go back to an alcohol injected, turbocharged engine. At zero boost, the engine is basically following the same criteria as a naturally aspirated engine. The intercooler, unless it's been iced, is not heating or cooling the intake charge beyond ambient. We won't be getting the equivalent hp out of the engine though, due to the lower static CR that must be run because of the plan to boost the dynamic CR way above what any static CR could ever provide in a naturally aspirated only application. Due to the lower static CR of the turbocharged engine, at off boost operation the air/fuel charge won't be properly heated during compression and the resulting vaporization and power will suffer for it. Not terribly, but noticeably.
Now let's step up to boosted operation. We can't argue that as the turbo compresses intake air, it's being heated. The more boost, the more heat. The heat that is added is preheating the air before it enters the combustion chamber. In a low boost, low static CR situation, that added preheating of the intake air is helpful to vaporize the fuel. What is the intercooler doing to the intake charge temp at this point? It is cooling it. Possibly down close to ambient temps. Depending on how much boost we have at this point, it could be hurting us if the dynamic CR has not started to heat the air/fuel charge to a proper level for good vaporization of the fuel. This will hurt spool up time.
Now let's move to high boosted operation. The turbo is heating the intake charge to very high temps. Let's say 300 degrees F. Depending on where our static CR was set and the boost level, our dynamic CR is probably going through the roof! Much, much higher than any high compression, naturally aspirated, alcohol injected engine could ever dream of attaining. It can calculate out to 30+:1 in some static CR/boost combinations. How much heat is the dynamic CR at this high boost level adding to the air/fuel charge during the compression cycle now? It is a lot! And remember, we started out with air temps of over 300 degrees out of the turbo, then compressing that in the cylinder with a dynamic CR of over 30:1. Can anyone say, what's the autoignition temperature of methanol?
You have four choices to reduce air/fuel charge temps to below autoignition levels:
1)Reduce the static CR.
2)Reduce boost. Who wants to do that!
3)Add more methanol, which will act as a chemical intercooler for you. It will not be burned, because there are only so many oxygen molecules in the combustion chamber. In fact, the extra methanol will be taking up room in your combustion chamber that should be used for more of a balanced air/fuel charge. The extra fuel also makes ignition more of a problem. Magneto anyone?
4)Or, use an intercooler along with a less rich mixture. Still using the help of the chemical intercooler, because the intercooler can't do it all alone.
Who wants that intercooler now?
Not the guys that are the fastest in the country.
But what the heck do they know
Speaking of the fastest in the country. Have you ever heard of the fastest VW dragster in the country? They burn methanol, spool with nitrous, have a static CR of 6.5:1, and use a liquid INTERCOOLER! Imagine that. I guess they haven't heard that the intercooler is slowing them down.
In fact, they recently set the record at our track.
Makes you want to read over my last post with a different perspective, doesn't it?
You wouldn't believe me if I told you how much boost they run.
The only issue I recall ever coming up with methanol getting too cold was icing in the manifold on an endurance engine. I remember seeing some pics a long time ago of a normally aspirated V8 with mechanical injection into independent runners. They started out with the injectors right down against the head, then moved them up an inch or two, then again, and maybe again, on an engine dyno. Each time they moved up the methanol had more time to evaporate before hitting the port and the colder the manifold got, and the more power the engine made. The highest position was cold enough to have frost rings on the outsides of the runners, but they were worried about icing inside the runners during a race so they settled on a lower position. Can't remember where I saw those pics, though, sorry. Don't think you have to worry about ice buildup .
.80 psi is what I've read. It's gotten some attention.
VW Paradise is the shop.
Check them on You Tube.
The only issue I recall ever coming up with methanol getting too cold was icing in the manifold on an endurance engine. I remember seeing some pics a long time ago of a normally aspirated V8 with mechanical injection into independent runners. They started out with the injectors right down against the head, then moved them up an inch or two, then again, and maybe again, on an engine dyno. Each time they moved up the methanol had more time to evaporate before hitting the port and the colder the manifold got, and the more power the engine made. The highest position was cold enough to have frost rings on the outsides of the runners, but they were worried about icing inside the runners during a race so they settled on a lower position. Can't remember where I saw those pics, though, sorry. Don't think you have to worry about ice buildup
Even with intercooling the intake air temp will be higher under boost conditions than the ambient air temp your example engine was ingesting. The chance of ice buildup is far less.
The danger of having ice buildup on an engine with independant runners is the throttle blades sticking from the ice if the fuel is being injected before the throttle blades. In a turbo application, typically one throttle blade is used and it is well up stream of the area where the fuel is being injected.
My intake design gives me a unique opportunity to see what's going on inside the plenum. My port runners are higher than the floor of the plenum. Any liquid that might collect in the plenum settles to the bottom. I have a drain hose that I can drain to check on what's settling in the plenum.
On first startup on methanol (using a gasoline primer), the plenum will collect a mix of fuel and water. You can tell by putting a finger in the stream as it drains into a pan. If the stream is warm, it's water. When the temp of the liquid felt by my finger changes from luke warm to cool, the stream just turned from water to liquid methanol. This collection of fluid only occurs on a cold startup. After the engine has some heat in it and the plenum is heated, the rest of the day I can pretty much leave things alone.
The water and fuel I get after cold start is caused by icing. Remember, this is just idling with ambient air temp being ingested. Like a naturally aspirated application. This is also with an intake at ambient temp. When the engine is run hard, even with intercooling, intake air temp is high enough that water vapor cannot turn to ice. After a run, if I check the plenum, there is very little liquid that drains out. If ice was collecting during the run, it would have melted by the time I returned to the pits and I would have been able to drain some water from the plenum. This tells me that my intake temps are at least hot enough not to allow ice to form.
- Joined
- May 28, 2001
It's nice that people would make suggestions to others on how to configure their car or engine, but it should be backed up with some research of real information. Making a suggestion to eliminate an intercooler from one's system is a very serious suggestion. It could very easily mean the demise of someone's engine. If I made a serious suggestion like that to someone, I would make sure I was able to explain why or what changes to the tuneup would be needed to adjust for the change. All these people that are pushing to eliminate the intercooler, but not one is able to come up with any logical information to back up their point. Guys, this is very dangerous stuff (making tuning suggestions) you're playing with. I don't mind exploring other options, but it should be understood that it is uncharted territory for some. Concrete explanations should be offered when it's available. The statement that, 'This guys doing it, so you should' doesn't fly with me. I need more info than that.
et/mph f'in fast!
OK. Since no one is offering any good information in opposition to, or the defense of running an intercooler, let me offer this small methanol tuning tid bit.
First off. My disclaimer. It must be understood that every methanol engine is different and one tuning setup that works on one can be totally wrong for another. Tuning methanol is an art form. No engine is the same.
It is true that there is a temperature window that is optimum for the intake.
Too cold and you have methanol fall out. You must run richer to make up for this fallout, which cools the intake further, which requires more fuel, etc., etc. Mixture strength can be used to control intake manifold temp.
Too hot and you lose power due to the loss of charge density. The high temp limit has been documented as being 180 to 220 degree F.
Some supercharged methanol engines lean out the mixture on the top end. This is done to maintain the target best power a/f ratio. Explanation. As the engine runs down the track, the heated, compressed air from the blower heat soaks the intake manifold. As the intake heat soaks, the charge air density becomes less. To maintain the target best power a/f ratio, the fuel must be leaned as the air density falls due to the heat soaking of the intake manifold. Basically, the intake manifold itself acts as a very, very small intercooler that becomes heat soaked rather quickly. Many tuning tricks can be employed to control the rate of the intake manifold heat soaking. Just one of those tricks happens to be the use of an intercooler to take away much of the heat that would normally heat soak the intake. With the rate of charge air heat increase hitting the intake manifold lessened, the rate of heat soak of the intake is also lessened. On a long run, the liquid intercooler would eventually heat soak and the rate of intake manifold heat soaking would sharply increase. That can be delayed by playing with different icing levels of the water for the intercooler. Remember. We don't want the intake too cold at the start of the run. But, if the intercooler isn't iced at the start of the run, then it isn't changing intake air temp beyond what it would be if there wasn't any intercooler at all. But, having the intercooler with ambient water temp will control the rate of intake manifold heat soaking. Basically, by running the intercooler, we have increased the very, very small intercooling capacity of the intake manifold.
I hope this makes sense.
First off. My disclaimer. It must be understood that every methanol engine is different and one tuning setup that works on one can be totally wrong for another. Tuning methanol is an art form. No engine is the same.
It is true that there is a temperature window that is optimum for the intake.
Too cold and you have methanol fall out. You must run richer to make up for this fallout, which cools the intake further, which requires more fuel, etc., etc. Mixture strength can be used to control intake manifold temp.
Too hot and you lose power due to the loss of charge density. The high temp limit has been documented as being 180 to 220 degree F.
Some supercharged methanol engines lean out the mixture on the top end. This is done to maintain the target best power a/f ratio. Explanation. As the engine runs down the track, the heated, compressed air from the blower heat soaks the intake manifold. As the intake heat soaks, the charge air density becomes less. To maintain the target best power a/f ratio, the fuel must be leaned as the air density falls due to the heat soaking of the intake manifold. Basically, the intake manifold itself acts as a very, very small intercooler that becomes heat soaked rather quickly. Many tuning tricks can be employed to control the rate of the intake manifold heat soaking. Just one of those tricks happens to be the use of an intercooler to take away much of the heat that would normally heat soak the intake. With the rate of charge air heat increase hitting the intake manifold lessened, the rate of heat soak of the intake is also lessened. On a long run, the liquid intercooler would eventually heat soak and the rate of intake manifold heat soaking would sharply increase. That can be delayed by playing with different icing levels of the water for the intercooler. Remember. We don't want the intake too cold at the start of the run. But, if the intercooler isn't iced at the start of the run, then it isn't changing intake air temp beyond what it would be if there wasn't any intercooler at all. But, having the intercooler with ambient water temp will control the rate of intake manifold heat soaking. Basically, by running the intercooler, we have increased the very, very small intercooling capacity of the intake manifold.
I hope this makes sense.