Turbo Theories and Myths

[1100]

So what does a 66 frame with your greatest flowing internals compare to in the garret world, 2871, 3076?

 

[BAP]

well i am not the greatest tuner around, but I decided to put an aerocharger on my 2011 e-tec in january. Im at about 1700 feet but like to go to the mountains too. Had a few issues and one that i cant solve is this midrange popping/backfiring thing. So if anyone has cured this satisfactorily please let me know. I have no intercooler, a one piece silicon charge tube, and the new reed valves. I also had a spark plug come loose in the beginning and the electrode vibrated off, so i pulled the head and noticed the mag side piston was almost melted/finished. So I installed two new dual ring pistons and added 30 thou base gasket to bring the compression down for my altitude (running pump gas 91) engine now seems to be fine and probably have about 700 miles since that. On differrent rides I keep tinkering and think I have the clutching pretty good but the pipe finally cracked open I think due to the backfiring....anyway I welded that up and am back to the same problem. seems when its cold outside it works really well with hardly a backfire.....but in warmer temps just cant seem to make it go away with the available fuel settings........shes awesome when she runs right though. But yes I agree with alot of others that have had problems and there is no help...especially out here in the boonies.....but it seems like the timing can't adjust quick enough when the extra fuel kicks in or something....or its just tooo much fuel when it turns on the injectors and theres not enough adjustment to correct it.......or something.

 

[BAP]

oh yeah and when the boost starts (if yu clamp it) it spikes to about 6 lbls then settles back to about 4 and a half @ 8000. a/f is anywhere between 11 and 13 depending on the day.....but reguardless it still farts around before it catches and especially from a dead start. But if its cold it very seldom happens. Nonetheless its still frustrating as hell.......

 

[mctrailboss]

If you are running an aerocharger you should look to make sure the blue light is coming on when boost is present. I had this problem at first and when diagnosed they sent a new controller and its been perfect ever since. If you find the recommended settings from aerocharger are way off and your adding a lot more fuel recommended this could be it. hope that helps.

 

[BAP]

well the settings seem alright and the blue light comes on and everything.....you can lean it out on the a/f....im gonna **** around with it today again for a bit and double check a few things maybe spark some new ideas.

 

[BAP]

ya.....i see what you are saying i think....im down at the other end and can't seem to get the setting low enough on warmer weather.....at the transition point that is.....it seems the sputter/backfire happens right when the blue light comes on or very slightly before. If you are just riding with smooth throttle applications everything seems to work great, but if you need to tap the throttle around or clamp it, it sputters and sometimes backfires.



There must be something i don't quite get with these fuel settings....

 

[BAP]

Well same crap, up and down and all around on that controller, got the knock sensor to go off for the first time, but no differrence, probably the last ride so ill pick it up again in december. Maybe ill try to sell it and go back to a yamaha....he, he. Sure alot less screwin around.

 

[E-Zmoke]

Well same crap, up and down and all around on that controller, got the knock sensor to go off for the first time, but no differrence, probably the last ride so ill pick it up again in december. Maybe ill try to sell it and go back to a yamaha....he, he. Sure alot less screwin around.

Why not just take that dobeck fuel controller off and throw it in the trash and buy a Boost It controller?

 

[BAP]

Ya, I'll have to check pricing and stuff, and try to find out if it will cure this, and try to find out if anyone else has had these kind of problem. I guess I should try to phone that Kyle(i think) at TSS over the summer sometime as it seems he may be able to help out if he doesn't mind sometime.

 

[Deano670]

The electronic position sensor for the raves can cause these problems especially of the boost isnt being bled off properly and pushing the raves outside their normal working positions. That sensor has an affect on fuel and timing.

Deano

MAD MOTORSPORTS

 

[sick1]

sounds like rave valve position.. make sure you have a one way valve off the carbs to the raves.. i had a major bobble on my 11. put the one way valve in and was 100% better.

 

[lilduke]

I have been reading through this post and I had a few things I wanted to make discussion of...

I kinda disagree that sizing the turbo is different for a sled than a car (i mean, I agree it is different, being small displacement two stroke, vs a a 4 stroke car engine). But the general principles are the same arent they? the turbo is an air pump (as is the engine), spun by wasted exhaust energy (heat mostly, then pressure to a lesser extent). I dont feel that the issue is that a larger turbo compressor will increase the heat of the charge, more likely that you can get surging/stalling which can toast a turbos bearings/thrust bearing quickly. However a lot of compressor housings come with anti surge porting now which allow smaller engines to run much larger compressors without surging (like some of these car guys making 800+ hp on a 2L engine or even 1500hp on a 3L engine). Conversely an undersized compressor will choke causing it to increase in backpressure, overspeed at high rpm , blow oil seals, etc. In saying all that, imo there isnt really a reason to go with an overly large compressor on a sled anyways because even if you can spool it by a useable rpm, how much power is really necessary on a sled before you just flip over every time you nail the throttle. lol

Whats important and often overlooked is the Density ratio, which you mentioned in different terms i guess, by mentioning altitude and temperature. But those things are also of major importance to an automotive application as well.

Correct me if im wrong... I just wanted to join the discussion to learn more about sled applications

Why do you think heat has more to do with spining the turbine then the exhaust preasure?

turbines—machines that capture energy from a moving liquid or gas ie Kinetic Energy (moving energy)

Hook a turbo to an air compressor and observe what happens. Then unhook it and go throw it in the
Oven at 450 and observe.....

 

[lilduke]

NM,
I tried to explain why a turbo that is too big will have higher charge temps, but let me break it down at little bit more. I do love explaining this stuff so, here it goes and please anybody feel free to ask questions.

A compressor map is like a topo map. The top of the “mountain” is where you want to operate the turbo. Like a mountain there is a ridge, and as you go up in altitude or increase boost, you move along this ridge. You always want to operate as high on the “mountain” as possible. If the turbo is matched correctly you will always stay on the ridge as you change boost and/or altitude. By using a bigger turbo, you will be operating lower on the “mountain” than is best. The lower on the “mountain”, the lower the compressor efficiency. The lower the efficiency, the more heat the compressor makes at a given boost or pressure ratio. The higher the heat, the lower the air density is - therefore less oxygen to burn with the fuel. Less oxygen and fuel = less hp.

Engine load has nothing to do with compressor size as we do not care about compressor efficiency anywhere but 100% throttle on a CVT. A bigger turbo would only perform worse at less than 100% throttle, because it is even less efficient at part throttle then 100%.
With over 300 Aerocharged E-tecs, we can recommend 12.5-13 AFR - any more fuel than 12.5 and the E-tec is not happy. Your Pro will take more, but not the E-tec.

You said your AFR starts at high 12’s and creep down to low 12’s to save the motor... Does the boost-it box have a timer and add fuel as 100% tps is maintained? What if the pull is longer then you planed- does it keep adding fuel? We have run 30hrs straight at 100% with no issues. My guess would be your system is heat soaking and that is the cause of the creeping AFR. As the system heats up, the system has less oxygen and needs less fuel.

174 x 3 is a popular upgrade and we have many systems running this combination, including some in Revy without issues.

The race circuit is where I get to play with new technologies that do relate to back country riding weather at 11,000ft in Colorado or in Revy. Carl Kuster will be servicing and stocking kits at his CKMP in that neck of the woods. He puts on about 4k miles a year…lucky dog.

Hi Brad. Could you please explain the physics of why a turbo operating outside of its peak efficiency range would produce a higher charge temp?

To say a turbo creates higher charge temps when operating "lower on the mountain" really doesnt explain at all where this rise in tempature is coming from.

This is a turbo Theories and Myth thread after all...

Thanks

 

[lilduke]

NM,
I tried to explain why a turbo that is too big will have higher charge temps, but let me break it down at little bit more. I do love explaining this stuff so, here it goes and please anybody feel free to ask questions.

A compressor map is like a topo map. The top of the “mountain” is where you want to operate the turbo. Like a mountain there is a ridge, and as you go up in altitude or increase boost, you move along this ridge. You always want to operate as high on the “mountain” as possible. If the turbo is matched correctly you will always stay on the ridge as you change boost and/or altitude. By using a bigger turbo, you will be operating lower on the “mountain” than is best. The lower on the “mountain”, the lower the compressor efficiency. The lower the efficiency, the more heat the compressor makes at a given boost or pressure ratio. The higher the heat, the lower the air density is - therefore less oxygen to burn with the fuel. Less oxygen and fuel = less hp.

Engine load has nothing to do with compressor size as we do not care about compressor efficiency anywhere but 100% throttle on a CVT. A bigger turbo would only perform worse at less than 100% throttle, because it is even less efficient at part throttle then 100%.
With over 300 Aerocharged E-tecs, we can recommend 12.5-13 AFR - any more fuel than 12.5 and the E-tec is not happy. Your Pro will take more, but not the E-tec.

You said your AFR starts at high 12’s and creep down to low 12’s to save the motor... Does the boost-it box have a timer and add fuel as 100% tps is maintained? What if the pull is longer then you planed- does it keep adding fuel? We have run 30hrs straight at 100% with no issues. My guess would be your system is heat soaking and that is the cause of the creeping AFR. As the system heats up, the system has less oxygen and needs less fuel.

174 x 3 is a popular upgrade and we have many systems running this combination, including some in Revy without issues.

The race circuit is where I get to play with new technologies that do relate to back country riding weather at 11,000ft in Colorado or in Revy. Carl Kuster will be servicing and stocking kits at his CKMP in that neck of the woods. He puts on about 4k miles a year…lucky dog.

Do to the nature of this thread I have to correct you on this point tho. Yes warmer air is less dense than colder.True

However this has everything to do with intake air temp, not charge air temp.

A turbocharger draws in air from outside into a CLOSED SYSTEM. Air is made up of 99% of the Di atomic molecules N2 and O2(79% nitogen,, 20% oxegen). Once the air is in this closed system, there is no where for the oxegen to go execpt to the combustion chamber, no matter how much tempature it gains passing through the turbo.

Again go put an oxegen tank in the oven, it might explode but until it does there wont be any less oxegen molecules in the tank...

There is reasons for the higher charge temps hurting performance,, but less oxegen molecules aint it.....

 

[snopro]

Do to the nature of this thread I have to correct you on this point tho. Yes warmer air is less dense than colder.True

However this has everything to do with intake air temp, not charge air temp.

A turbocharger draws in air from outside into a CLOSED SYSTEM. Air is made up of 99% of the Di atomic molecules N2 and O2(79% nitogen,, 20% oxegen). Once the air is in this closed system, there is no where for the oxegen to go execpt to the combustion chamber, no matter how much tempature it gains passing through the turbo.

Again go put an oxegen tank in the oven, it might explode but until it does there wont be any less oxegen molecules in the tank...

There is reasons for the higher charge temps hurting performance,, but less oxegen molecules aint it.....

Holy crap!!! Are you Bill Nye the Science Guy? Lol.

 

[lilduke]

Holy crap!!! Are you Bill Nye the Science Guy? Lol.

Ha ha,,, Yeah Im guessing Brad is a sales man for Aero Charger not an engineer, But Id
still like to discuss some Turbo theories and myths with him tho

 

[CrankShop910]

Too bad Gus Bohne isn't on this site, his input would make this thread really interesting.

 

[oler1234]

Start reading... And do the math

theories, some ppl may agree and some disagree.

Sometimes it's more of a preference and what makes sense to that person with there current knowledge.

 

[lilduke]

Start reading... And do the math

theories, some ppl may agree and some disagree.

Sometimes it's more of a preference and what makes sense to that person with there current knowledge.

Yeah I definatly dont agree with alot of the theories at that site.

 

[DRD]

Semantics, 20.9 percent from sea level to the top of Everest, difference is the PsiA from these two extremes.