5 more psi=20hp? Tuners help

[esp3500]

Well I finally got enough miles on my new forged engine to add some more boost and try and improve on my 440 hp.
So I put a reichard racing 2.89 pulley on with a heavy duty tensioner and a gator back belt to bring my boost to 15 psi from the 10 that I had.

I just got back form the dyno. the first pull showed it was way rich in the top end, and my power was down to 395hp. so we started taking away fuel until we got it right and still had only had only 415 hp.
so We started adding timing ( remember we started with the same tune that made 440 hp adn 395 tq a month earlier)

We ended up at 21 deg total timing and 458 hp 427tq.

The only other thing I can add is that I did drop the compression to 8.6 to1 so I can run more boost and shoot some nitrous.

Question? how high can I go with the timing on pump Gas? 93 oct.

It just seems like a lot of work for such little gain.
and seat of the pants says its no faster. ( track day thursday will tell)

 

[rford426]

I am no expert but 21* sounds like a bunch for pump gas....my buddy runs 23* on e85 and that is considered alot to many I have spoke with...

 

[cmg427]

You dont need to up the timing you need to change your tuner and now

 

[Steedman07]

Brilliant..Just keep leaning it out and throwing timing at it....

 

[stkjock]

5# should be about 45-60 added HP

21* seems a but high At 15 psi and 93

 

[Simon]

5# should be about 45-60 added HP

21* seems a but high At 15 psi and 93

I think I run 23 or so at 16 psi and 100 octane. 21 @ 15 psi on 93 pump seems excessive.

Were your inlet air temps?

 

[BruceH]

9.86:1 at 10 psi has a dynamic boost compression ratio of 15.71:1.

8.6:1 at 15 psi has a dynamic boost compression ratio of 16.49:1.

In essence the net effect is an increase of .8 cr or 1.2 psi which is about 16 hp per psi from the increase. That's spot on. Low compression kills hp on lower boost motors.

 

[05stroker]

I would run a smaller pulley and less timing with 8.6:1. You need a lot of boost with a low cr motor to make power. I have a 9.0:1 and wish it was a 9.5 or 9.8 at this point. If I ever change pistons the cr will be raised some. I think there is some power left on the table when using race fuel with low cr. Now on pump, I think my 9.0:1 is the way to go. If you are lower then 9.0:1 you just need more boost to make up for the cr.

 

[burkem]

What is the advantage of a lower compression ratio? If it robs power then why do people choose that option? Im pretty new to how motors work and I am trying to understand all the ins and outs of performance engines.

 

[BruceH]

What is the advantage of a lower compression ratio? If it robs power then why do people choose that option? Im pretty new to how motors work and I am trying to understand all the ins and outs of performance engines.

It's safer with pump gas. My father in law was telling me that back in his day he used 6:1 pistons with an 8-71! You will still come across older guides that list max compression with boosted motors way below what we use in modern times. Back then they didn't have computers to control fuel and spark delivery so the motors couldn't be run close to the edge like we do now. The thought of lower cr with boost has still stuck around but in the last few years the acceptable cr has gone up.

 

[aleborjas]

throw there a 10% overdrive... wake up that engine with boost!

 

[Speed+Clinic]

Way too low compression... throw in more psi and listen to the knock sensors.

 

[JeremyH]

Plus one for iat's? Also what is your current fuel system?

 

[Fullboogie]

It's safer with pump gas. My father in law was telling me that back in his day he used 6:1 pistons with an 8-71! You will still come across older guides that list max compression with boosted motors way below what we use in modern times. Back then they didn't have computers to control fuel and spark delivery so the motors couldn't be run close to the edge like we do now. The thought of lower cr with boost has still stuck around but in the last few years the acceptable cr has gone up.

That and the fact that today's combustion chambers are so much more efficient, and we have aluminum heads. All that adds up to the ability to increase CR on a blown engine.

 

[Swarzkopf]

What was AFR during the dyno runs?
Sounds like, as everyone else has said, you need more boost with that CR.

 

[2005wantAB]

this is good info! I am looking at going max 13 - 14 psi centrifacal in the near future you hear all kinds of stuff on cr but it looks like it matters how much your going to push the boost on 93

 

[esp3500]

The iat never got over 100 deg. the final AFR's were about 11 to across the rpm range.
Also the fuel system is 39lb inj and gt500 pumps
I was copying the 2010 roush 540r interals when I built the engine because I figure if they can make 540 flywheel and give a 3 year warrenty, it should take my 500 rwhp.
overdrive pulley wont work because the intercooler tubes are too close to the crank pulley.
That only leavse a smaller sc pulley, and I think it would have belt slip problems then wouldn't it?

 

[RiskyBiznes05GT]

Move those lines and make room for od pulley. Trying to go smaller on the blower pulley is going to get you some nice belt residue build up around the Snout lol

 

[05mustang_TT_charged]

What was the duty cycle on the Injectors? They are only good for 525 rwhp or close to it.

 

[Swarzkopf]

the final AFR's were about 11 to across the rpm range.

11.0? That's on the fat side for your setup. You might see gains getting it to the 11.5-11.7 range. Was AFR determined from a wideband near your headers or from a tailpipe clip-on type wideband? If you were seeing 11.0 AFR at the tailpipe, you're probably running really rich.