Mikelly Posted October 15, 2000 Share Posted October 15, 2000 OK Guys, I know I'm not going crazy now... I have a Hayden adjustable electric fan switch I cranked up so the fan wouldn't come on until it wouldn't come on before 210 degrees. I was in traffic yesterday after warming the car up, and I noticed the throttle was a bit cripser with the temp gage houvering at 200 degrees. I also noticed that the car was running great at 1500RPMS in 6th gear. Car pulled strong in every gear, and ran perfect. Then I get out on the highway, and after I get moving out on the open road, no cars or stoplights, the temps drop to around 170-180. Car starts running worse.. won't pull 6th gear at less than 1900RPMS... My hypothesis: I'm dropping a 195 degree temp thermostat in the car today. I was floored at how well the car ran and how much more horsepower the car made when it was running a bit warmer... 15-20 degrees rise in temp made a HUGE difference.. See the post in "I'm Telling You" about yesterdays battle with a WS6 Firebird while the temps were in the 200 degree range... Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted October 15, 2000 Share Posted October 15, 2000 Great to hear it's running a lot better for you Mike:-) I've always preferred 185-190 temps, seen discussions on what's optimal but never seen a sound conclusion. anyhow, see if this makes sense: -throttle response and power is better when you're going slow/city speeds and temp's are up -your engine (I'm assuming you have our usual hot air intake on top like 99% of us) is getting hotter/less dense air when your temp's are higher (rad heat coming off is greater as is all convection from block) -I wouldn't be surprised if you're experiencing the differences in A/F ratio/ air changing 50+degrees can make (your underhood/intake air{1% power gain per 10 degrees) and your carb is jetted just right for the hot air but leans out beyond the power band w/ the cooler air once you're moving for a while? -have your plugs always been v. clean? anyone running behind you smelling richness? (doubt it) -just a thought, easy enough to check if one 'stage'/step richer improves 'cool' running you'll know, FWIW I can't make my temp's hit 180 on highway with my rad, with the Stewart water pump they spec a Robert Flaw HiFlo 'stat which has 1/8" bypass holes so pressure doesn't build up too high in the block. THis bypass is enough at highway to keep me closer to 160 if not lower (stock temp guage) FWIW. I'd have to block off some radiator to change that, that'd be a switch eh;^) Quote Link to comment Share on other sites More sharing options...
Mikelly Posted October 16, 2000 Author Share Posted October 16, 2000 I'm not sure, but one thing I noticed when the temps were high on the open road with no obstructions and cool air coming in, the car was making stable HP enough to pull at 1500RPM in 6th gear. I think what is happening here is an issue with aluminum heads and compression/ combustion maybe? All I know is that my car will not pull 6th gear at less than 1900RPMS when the motor is at 190 degrees coolant temp or less. But when it is at 200 degrees or more, car loaps along at 1500RPM in 6th gear... What I think is happening is less gas is going into the headers and exhaust, less loading up in 6th gear. My plugs always look light brown, so I'm not sure, but I think the car is running well overall, but would benefit from higher temps... Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted October 16, 2000 Share Posted October 16, 2000 Ross, just an FYI - Mike has an airbox ram air type setup - he's not pulling hot air in from on top of the motor - it's coming from up front by the radiator. Hotter engine temps ought to maybe vaporize the fuel better. I really do think the engine shoudl be run warmer rather than colder. The only reason why folks with EFI engines put in cooler thermostats is because the fuel curve is richer at cooler temps and when you've done some mods the engine needs the richer fuel mixture to compensate. Tuned correctly the motor, especially with aluminum heads, ought to like hotter temps. Quote Link to comment Share on other sites More sharing options...
Rob Posted October 16, 2000 Share Posted October 16, 2000 I think you are definitely on to something Mike. I bought a book by Smokey Yunik, race tuning guru from way back, and he talks about cooling temps. Below is some plagarism from his book Power Secrets: Keeping the engine cooler than is necessary puts energy that could be used for power in the radiator. "Running an engine at 180 will drop overall horsepower 2-3%. For max power the coolant temperature should be at least 200, and you should have at least 25 psi in the system. Actually a racing engine like the small block chevy will produce more power as the operating temp is increased to a maximum limit of 220. This can be confirmed with dyno testing, but I would not unconditionally recommend that any engine be raced at 220. This leaves very little leeway for variations in the operating environment." Back to your original comment, you mentioned a huge difference. Smokey mentioned 2-3%. It could be that your mixture is richening a little due to a hotter manifold, and perhaps you were a tad bit lean at the 170-180 coolant temp. Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 16, 2000 Share Posted October 16, 2000 Now to get a bit off topic: Rob, anybody, do you remember a Hot Rod magazine from like 15-20 years ago that had an engine that Smokey put into a Fiero that used pre-heated and "homogenized" fuel-air into the combustion chamber? I seem to remember him heating the fuel-air with the coolant, using a low pressure turbo to "homogenize" it, and then preheating it again (with the exhaust manifold)? I think it was called "Smokey's Hot Air Engine". I never did figure out if it was hocus pocus or not, but I have a lot of respect for him, so I kind of believed it. I never did hear about it again. ...Well, I just answered my own question kind of. This guy (T.O.O.) didn't believe it either. I had the same feeling about the "positive pressure" in the intake that Smokey said was just to get the mixture into the cylinder. Seems like this guy agrees that really was boost, and the power increases came partly from that. My point in bringing this up is that Smokey describes his reason for doing this whole project from "looking at high school physics books". Well truth be told, I didn't really get what he was talking about until I go into Thermodynamics class in college. I learned about the perfect (Carnot) cycle engine and how a higher mixture temp at combustion was better for power and efficiency. Then it made sense. Sorry for the ramble, I was just wondering if any of you remembered this. I do think that Mike's problem has to do with the carb though. Mike, have you tried bolting another carb on it for kicks? I have a rebuilt 750 vac sec sitting on my motor that I'd hank for you to try. I also have a 600 vac sec that you could borrow, just to rule out the carb. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted October 16, 2000 Author Share Posted October 16, 2000 Thanks for the offer Pete, but I don't have a vacuum advance on my distributor. I also suspect that my carb is in better target tune, basedon what I noticed this weekend. I think the temps are playing a direct role in my lean/ rich issue. I've got the carb tuned to a better baseline now and hope to keep it there! We'll see. Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted October 16, 2000 Share Posted October 16, 2000 Just curious Mike - why no vacuum advance? I'd think that would help part throttle cruise - is the vacuuum that low? Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 17, 2000 Share Posted October 17, 2000 I'm with Jim. Isn't it a misconception that the hot ticket is to disable the vacuum advance (or not have one) if you are driving the car on the street and want part throttle response? Yeah the racers go without it, but part throttle is not in their interest. I'd think that vacuum advance might even be the culprit as to why the motor has trouble at times with the 1600 rpm 6th gear cruise. I read about the vac advance on the street thing all the time. It seems like everything I read says that unless you are racing all the time, vacuum advance is the way to go on the street. Unless you have a computer doing things for you and reading MAP sensors and the like. I've tried going without vacuum advance, and even with a 3300 lb car with a 240 deg @.050 cam, it liked having the vacuum advance. Quote Link to comment Share on other sites More sharing options...
Rob Posted October 17, 2000 Share Posted October 17, 2000 No Pete, I don't remember that induction system. The cool thing about Smokey is that he wasn't afraid to try anything. A lot of the stuff didn't actually work I think, but enough did to make him a legend. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted October 17, 2000 Author Share Posted October 17, 2000 I have an MSD Billet Mechanical distributor. I was told that it was a much better way to go and very tunable. Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 17, 2000 Share Posted October 17, 2000 Mike, what's your timing at 1600 rpm? The issue is it's not much probably, unless it has a REALLY quick curve in the weights/springs setup, and you might not want that anyway. The issue is that when you're at 1600 rpm, it might not be getting much advance and that could be causing the lugging, etc. That's cruise condition at those rpm is exactly what vacuum advance is for, as far as my experience and reading goes. Of course, the parameters (air temp, engine temp, humidity, etc.) can make that variable. As far as mechanical advance goes, when a distributor has light springs in it, it can tend to be not too repeatable as to the timing curve from one accuation to the next at low rpm. The trade off in setting this up is balancing the spring tension and weights. Just wondering if this could be a problem as well. I don't know if you've considered any of this, but just in case you haven't, I figured I'd put it out on the table. Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted October 17, 2000 Share Posted October 17, 2000 quote: Originally posted by pparaska: Mike, what's your timing at 1600 rpm? The issue is it's not much probably Pete's nailed this one on the head a few times now. NO vaccuum advance is pretty much for full race only. Yes disconnect the vaccuum to simplify tuning in the adjustable mechanical part to make sure it's not playing any error into your settings. But usually only q in tuning is if you want to run ported or full vac. advance, not vac. yes or no. Same difference as driving any vehicle with zero or like 2 degrees initial compared to say 12 or 14 (L28 or v8), one's a lumpy dog and the other runs like a raped ape. The overdrive trans are getting more common now but raceshops/builders aren't always used to this, they may have thought you had a 4spd or TH350 where you'd be doing 3000rpm and have full mech advance of 36degrees on the highway, instead you may be at 20 degrees, whereas with vacc. you'd be at 30+. Mike, to simply 'prove' this to yourself just dial in another 5 degrees or more of timing BEING VERY careful to not stomp it AT ALL. (you don't want to put high load on it at this higher timing, it's fine at light to low load) Get it slowly warmed up and your highway response at 1600 will start to improve (given standard vac. cans are 10degrees and more, you're halfway to getting to a more 'normal' response). This will help confirm it to you. Dragrace only cars etc don't mind your dizzy as they have NO use for the vacc. advance. It's v. good to fully understand all aspects of timing before going with a fully adjustable/and/or custom setup as all aspects have significant roles and when you deviate from a standard setup it can be hard to know the full impact of your changes. Dr.'s Guide to Optimizing your Ignition is v. good as are many web URL's, none handy at school here. [This message has been edited by Ross C (edited October 17, 2000).] Quote Link to comment Share on other sites More sharing options...
alsil Posted October 17, 2000 Share Posted October 17, 2000 Actually, I noticed the same thing on my old Mustang I used to have. I used to race the car and didn't even have a vaccuum hose anywhere near the engine (I didn't like 'em). I stopped racing and drove the car like that for a while, and got really crappy gas mileage and throttle response. One I got above about 2000rpm, the car would rocket. I scratched my head for a while, and finally realized there was a reason for that vaccuum canister sticking off the side of my distributor. I hooked up a hose, and noticed better response and about 3mpg improvement. I also had to back off total timign because I had 289Hipo heads, 10.5:1 compression, which would ping easily. That may not be the issue with your engine considering compression. Having on the edge of detonation is usually the best place to have it if there's a problem. Just my 2 cents. ------------------ http://refuse.netdojo.com/Zcar Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted October 18, 2000 Share Posted October 18, 2000 Hrm, guess I shoudl take my opwn advice an dhookup the hose on the L6 that's in the car now huh? Quote Link to comment Share on other sites More sharing options...
Guest Jason Posted October 18, 2000 Share Posted October 18, 2000 quote: Originally posted by pparaska: I seem to remember him heating the fuel-air with the coolant, using a low pressure turbo to "homogenize" it, and then preheating it again (with the exhaust manifold)? I think it was called "Smokey's Hot Air Engine". I like the idea of using a turbo to homogenize the fuel air mixture. I think preheating the mix is a bad idea though. About engine temps, I've read that hot oil and cool water make the most power. David Vizard, author of this SBC book I have claims elevating oil temp from 180 to 210F is worth about 5hp, and independently dropping water from 200 to 170F is worth 6 or 7hp on a typical 300hp SBC. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted October 18, 2000 Author Share Posted October 18, 2000 This is why I love this website... lots of smart people with lots of good information! Pete, I don't know what my timing is at 1600rpms, but I will check it. I have one medium spring and one light spring in the distributor now. Before I started playing with the timing I had two heavy springs in it and only about 11 degrees timing advance. I might get rid of the light spring and put another medium one in and see how that works, we'll have to see. I popped in the 195 degree thermostat last night and I'm gonna take it for a spin this evening and see what happens. I know in some configurations it is important to get coolant temps way down, but I swear guys, the car was running SO MUCH better with the temps right at 200 degrees. I suspect my combo of parts is just plain happy operating in that zone. As for using the mechanical distributor, I heard pros and cons before I bought it, and I spoke with several guys who were using it on the street. All said once it was dialed in, it worked great. So I'm inclined to just continue playing with it, like the carb, until I get it right! Keep the flow of info coming! Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
MYRON Posted October 18, 2000 Share Posted October 18, 2000 Yeah, Funny thing, My dad would always raz me about trying to keep my car temp way down and all the 160 degree this and that. He used to race cars for Bondini and a few others back in the day in Europe. He to this day tells me that the optimun operating temperature is 210 for most gasoline powered engines.. My car too is more responsive at 200 degrees, but with the stock radiator I am affraid to run it for long at 200.. Myron Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 18, 2000 Share Posted October 18, 2000 I'd check the mechanical advance curve first, using a timing light and tach. See how much advance past the intiial timing you have at 1600 or so and then decide. You may find that you need to advance it quicker to get the timing a bit more advanced at 1600 than it is now. This is a good way to test for repeatability as well. Do a timing curve test a few times to see if the springs/weights are hanging on some of the tests. I've had a problem with that with the L6 distributors before. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 31, 2000 Share Posted October 31, 2000 Just anouther FYI. You can retain that heat you like in the combustion chamber longer by coating your piston tops and valve faces, as far as that goes you can really do it up right by coating your combustion chamber dome. This makes for a much cleaner hotter burn, without transfering all that heat to your block and heads, not to mention that it also extends the life of your parts. THIS HAS BEEN ANOUTHER SHAMELESS PLUG BY THE TAKMAN,,, HE HE . LATER GUYS, Tony ------------------ My Z is unfortunatly on the back burner,due to the shop,but not to much longer!! www.speedtechcoatings.com Quote Link to comment Share on other sites More sharing options...
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