20g Qestion

[-red97rum-]

Actually he is much much closer than you think.

Other than the change in intake charge temp and volumetric efficiency (on the hot side) 15 psi is 15 psi in the manifold. This is of course assuming everything is equal.

Somebody post up a link to the old threads about this....the one with the discussions on VE and all that jazz. I will do it when i get off work if noone else finds them.

(Hint I wrote a good portion of the thread)

You need to read the entire thing all the way through to understand what 40 is saying.

I think you mean this thread: http://www.dsmtuners.com/forums/showthread.php?t=1169&highlight=turbos+boost+level -and I have read it.

Agreed. My post was a bit sarcastic and I apologize for that 40. I do understand that the engine is a "restriction" so to speak, and if a certain turbo can move more air at the same pressure as a different turbo, it still must pass through the same restriction (engine). But I'm referring to real world results that I've experienced, a 14b @ 15psi vs a b16g @ 15psi makes a difference.

I just think he should have explained himself better, and thats why I said he was posting misinformation, I think I did it to provoke a more detailed response if anything.

Cheers, it's Friday!!

 

[crankbender]

I think you mean this thread: http://www.dsmtuners.com/forums/showthread.php?t=1169&highlight=turbos+boost+level -and I have read it.

Agreed. My post was a bit sarcastic and I apologize for that 40. I do understand that the engine is a "restriction" so to speak, and if a certain turbo can move more air at the same pressure as a different turbo, it still must pass through the same restriction (engine). But I'm referring to real world results that I've experienced, a 14b @ 15psi vs a b16g @ 15psi makes a difference.

I just think he should have explained himself better, and thats why I said he was posting misinformation, I think I did it to provoke a more detailed response if anything.

Cheers, it's Friday!!

There are quite a few threads similar to this one. I will attempt to explain in a simple matter as my skill at conveying information has sharpened. Does anyone else hate going back to their old posts and reading them? I find mine to be wordy and confusing at times.

OK here goes.

Assume everything remains the same from example to example.

As your engine rotates a given volume and pressure of air will be in the cylinder when the intake valves close at any given RPM.

There are 2 ways to increase the mass of oxygen and, therefore, increase the mass flow of air (make more power).

#1 decrease the temperature
#2 decrease the ammount of exhaust that was left in the cylinder after the exhaust valves closed.

The only gain you get from changing turbos without changing pressure are changes in the intake charge temp and exhaust holdover. Considering that the exhaust usually makes up less than 15% of the engine volume (and rarely if ever decreases to 0 on a turbo car) it can generally be said that 15 psi is 15 psi.

 

[prophecy7115]

Ok i just finished my 20g setup, i hope its ok i have stock fuel so i really havent pushed it, the minimun acuator is set at 18psi. Ihave stock fuel and i know that my knock sensor is kicking in so i really dont expect much, But it feels good when it does run.

 

[crankbender]

18 psi on stock fuel is baddddddd.

Fix that asap

 

[40oz]

I think you mean this thread: http://www.dsmtuners.com/forums/showthread.php?t=1169&highlight=turbos+boost+level -and I have read it.

Agreed. My post was a bit sarcastic and I apologize for that 40. I do understand that the engine is a "restriction" so to speak, and if a certain turbo can move more air at the same pressure as a different turbo, it still must pass through the same restriction (engine). But I'm referring to real world results that I've experienced, a 14b @ 15psi vs a b16g @ 15psi makes a difference.

I just think he should have explained himself better, and thats why I said he was posting misinformation, I think I did it to provoke a more detailed response if anything.

Cheers, it's Friday!!

A larger turbo at the same boost can be a big difference if the engine already has a few mods to increase VE so that the current turbo is definitely too small. Bigger exhaust, better intercooler, etc. In that case, the 14b would be really huffing to provide 15 psi, so it would be terribly inefficient, heating the air a lot. Also, sorry if I didn't make it clear that the larger exhaust housing on a bigger turbo would increase VE. I mentioned that a time or two but it wasn't very apparent.

All in all, I would say my posts are definitely not misinformation; I would actually counter and say that the people preaching otherwise are the misinformers.

18 psi on stock fuel is not good.

 

[prophecy7115]

I completly agree. I am sorry for bieng hard headed. Just like people stated on my 20g turbo with stock fuel will not run as efficeint or as well as my stock turbo are correct. The turbo spools quick but the car runs slow, My calculations are that the knock sensor is put to work retarding the timing, thus slow acceleration. I havent pushed past 4k, But feel a quick power burst when i feather the accelerator, I believe because the car runs out of loop when i let of the WOT setting hte timing back to place. But i really hope this car runs normal once i put the safc injectors and pump with intercooler in. Because right now the car isnt running to well.

All of these things that accured are based on 2 runs at wot in second gear to 4k. Since i have driven the car under 5psi (throttle controled) I do not run the car hard, so dont think i always WOT.

 

[GS><]

Wow that is amazing that the car wont make More power with a bigger turbo unless the turbo is out of its efficient range. I thought that 15 psi with a 20 would be alot More power then 15 with a 14b or 16g. I was always told that there is alot more airflow with a larger turbo. Learned something new today!!


John

 

[doug]

That's just because he doesn't have the necessary supporting mods for that turbo. Otherwise, the power would be there.

 

[Spoolin4Ever]

Too much air, not enough gas=Knock/detonation=Timing retard=slow. The knock sensor will detect knock, and the ECU will retard the timing. That slows your frickin car down people.

Or, you would get fuel cut.

Or you would melt a piston......

Keep off the boost and it's cool. Try to keep it in the 10 and under using the gas pedal to control it.

 

[prophecy7115]

Yea i am doing that, once again thanks alot guys. Alot of my questions have been answerd thanks to the tuners on this forum once again thanks. Ill let you guys know how it goes once the safc and injectors are put. Hopfully better thank they are now.