25psi ok if the fuel is there?

[andymoraitis]

Geez I can't even run 25 psi on pump gas with my 50 trim.

25psi on 93 octane
14:1 A/F at the onset of boost tapering to 11.5:1 at 4000 and above
12 degrees timing advance (don't try this on cast internals) with more timing in the midrange from 2-4K
42 psi fuel pressure
2 counts of knock
Dejon Sidemount and an EPROM ECU

I can run 28 psi on 100 octane or more than 30 on 110 (too bad the boost gauge doesn't go above that). Once the boost comes on, the car's a freaking blast.

 

[MyBeatGSX]

2 questions for you.

Why is very retarded timing bad for stock internals?

and

Isn't it generally true that timing makes more power than leaning it out? Why did you choose 11.5 and low timing instead of say 11.0 and a couple degrees more timing?

Not arguing or saying you're doing it wrong, just trying to learn something.

 

[andymoraitis]

Retarding the timing makes much more heat in the motor. Cast internals shouldn't be run below stock timing levels. The lowest safe repeatable timing I would consider is 16.

If you look at the methodology used to make more power on pump gas, it's always boost over timing. Granted, timing creates torque and gives the motor more grunt, but look at the following example:

25 psi with 12 degrees of timing
20 psi with 18 degrees of timing

More boost with less timing will make more power. than less boot with more timing. There isn't a big difference between running 11:1 and 11.5 in terms of power production, but I prefer to find where the tuning edge is (2-3 counts of knock) so that I know where maximum safe power can be made. If you call Buschur and SBR and ask them where they make big power it's usually between 11-11.5:1 at 12-14 degrees of timing. On race gas these guys run enormous boost and maintain fairly low timing.

While my total timing advance is fairly low, I do run more in the midrange than the stock maps to get the car moving and into that operative range where the turbo kicks in and it turns into a nice little street rocket. Keep in mind that I prefer a smooth boost hit. With lower timing and the linear nature of the 50 trim map, I can roll onto the throttle in 1st gear in the rain and not break the tires loose. It's soft and easy on the drivetrain parts too.

Look up a user named dre99gsx. He made 404 WHP on 8 degrees of advance running 93 pump.

See what I mean?

 

[MyBeatGSX]

See I did learn something. I just learned that I need more than an SAFC to tune with.

Making 300hp sucks. It was supposed to be EASY and CHEAP! ugh

 

[GVR4592]

2 questions for you.

Why is very retarded timing bad for stock internals?

and

Isn't it generally true that timing makes more power than leaning it out? Why did you choose 11.5 and low timing instead of say 11.0 and a couple degrees more timing?

Not arguing or saying you're doing it wrong, just trying to learn something.

Retarding the timing causes egt's to go up, most cast pistons can't handle high egt's as well as forged pistons. It could cause piston damage.

Advacing the timing will usually yield more power than leaning out the A/F. It really depends a lot of factors though.

http://dsmtuners.com/forums/showthread.php?t=230376&highlight=timing+torque

A/F adjustments usually don't make a huge difference in power when they are within the 11-12:1 range. If the mixture is much leaner or richer than that range, then it can make a signigicant difference.

I tuned an RX7 with a pretty decent setup a couple years ago, the base tune was very rich, around 9:1. The first pull the car made 246whp with a very crappy powerband and a lot of stuttering. The next pull it made 315whp just by leaning out to 11:1, this was at 8 psi on a pretty large turbo. The third pull I leaned it out to 11.5: and it made 316whp, the curve was almost identical to the previous run. So the first point and a half made a huge difference, but the next half point did almost nothing. I ended up with 11.2:1 to keep it safe and the power remained the same.

 

[GVR4592]

You beat me this time Andy. If I hadn't walked away from the computer for that glass of water......

 

[MyBeatGSX]

Well its good to know I probably didn't loose any power by going for 11:1 this time instead of 11.5:1 like last time.

That's a good link too, thanks.

 

[exiletalon]

hmmm.... the 300hp mark is the first significant acomplishment of the majority of DSMers!