I was wondering if it was better to have less boost and run more timing than have more boost and less timing...

I am running IATs in the 180s with 9psi or so and I have been unable to reach the power I wanted or expected out of the setup...

When I ran 4.5 psi and a small cam I did 406 @5140 rwhp now with a much bigger cam XE and 9psi i am running 463@ 5400, the difference is that, although with the 4.5 psi I had more or less the same IATs I was running 0 knock retard/psi with a total advance of 36º. Now I run total advance of 34º with a 1.5 retard/psi..

I have learned that this is all a combo... so when do you have too much boost for your app? and how do you choose the best combo between boost and timing??? they both make power as I am aware of...

 

Boost is better than timing for big power, i think you need a better intercooler or lower compression.

 

I got 9:1 now

 

Highlander, you and I are basically in the same boat.

You went from 4.5 to 9 psi + a cam and only picked up 55 rwhp (less than 12 hp/psi boost).

I went from 9 to 14 psi + much better heads and only picked up 40 rwhp (less than 8 hp/psi boost).


I tried some race gas and full timing (no boost timing retard) and picked up about 20 more rwhp, but that still only puts me at less than 12 hp/psi boost.

One thing that remains the same between our set-ups is the lack of intercooler. However, some people

www.96silverz.cz28.com

have made 622 rwhp with no intercooler and overall mild combinations.


So where does that leave us?

Based on MAF readings, we are both flowing plenty of air. So, my game plan is as follows:

1. Check exhaust backpressure using a pressure guage. According to Lingenfelter, anything over 5 psi is bad. I personally gained 40 rwhp by dropping from 9 down to 6 psi by changing the exhaust in my previous car.

2. TRY to check compression. Cracked and broken ring lands can relieve cylinder pressure. Plus, my car uses 1 quart of oil ever 400 miles, but that could be bad valve seals, intake gasket, etc.

Mike

 

The car with the 6-speed will always show a lot more HP on the dyno.... So I do not believe it would be a good comparison to your cars. Just my .02

 

We are talking about picked up HP..not about comparing hp with each other...

Anyways... I have a 3" borla...

I have hooker LT's and custom Y pipe, which I honetly LOVE!!! It comes from 2 3" to the borla that is 3". Now I have it completely shut on the right side for noise.. this thing is super noisy when you rev it... On the dyno I removed the blocking plate and gained 16rwhp...

Not bad.. I agree...

But anyways... I dont think there is a cracked engine.. 9:1 9psi and almost no detonation... all forged?? I dont think so, besides its a pain in the A$$ to do a compression check with the headers...

Anyways.. I am making the HP @ 5400 rpm.. this cam lives at 6000+ there are my other HP due to lack of fuel I haven't got there yet.. I will as soon as i get my 50s. For some reason this is a mega fuel hungry car.. .I will change my coil today and see if it helps.. I should have more than enough fuel but I dont and it consumes a lot of fuel... a lot!!!! a lot!!! I get 10mpg HIGHWAY so there is something wrong going on here...

 

What is your A/F? Why are you stopping at 5400rpm? Is it going way lean after 5400rpm so that you are not acheiving your max hp? What pulley combination are you running; where is your pulley combination maxing out? What is your head exhaust flowing at? If you don't have an aftercooler, when you are dynoing did they have a killer big fan to cool your engine and blow cold air?

If you are planning to go over 550rwhp, I would highly suggest the Acceleronics box and some low impedance injectors instead of the high impedance sloppy 50#/hr. The box and low impedance injectors are very easy to do. I was scare to do it before but after I did it, it was awesome and very simple. Now with 11# and the 72#/hr not dyno tune yet, I'm getting already 13 mi/gallon.

good luck

 

12.5 steady till 5400 then it will spike up to 13:1 in a straight line... My superfueler are maxed out.. I have 2 96 and one 34.8 in the superfueler...

The injectors looked to be maxxed out as I am getting 150% Duty cycle.. I am running a racetronix pump and i have no problems with it.. so its not the pump..

The box converter is a lot more money for now...

I have 1 3/4 headers no cats, custom 3" Y pipe and borla in the exhaust... Borla is a restriction, but I'm a bit worried with the fuel requirements... My graph is always climbing till I shut off... so I need more fuel...

7" crank and 3.1 blower pulley i am making 9psi at 5400 and 10psi at 6000, but i am not reving it there too much because of the fuel requirements...

I am running 60psi fuel press on idle and about 70-75 at WOT... so i dont know why I am out of fuel...

I am making 8-9mpg city and highway... I changed my coil (jacobs ultra coil 6year old, although super low mileage) to a new msd blaster coil.. the btm was sent to msd and sent back as perfect... so I should know now and if mileage goes up..

 

Coupla points:

1. You can't come to any conclusions until you have enough fuel to rev it until the hp stops climbing.

2. You obviously need more inector. To make 613rwhp with a 14psi non-intercooled S-trim, mild cam, mediocre heads, I was using 50's + 3x92lb'ers in the SF. And that was pretty close to maxing the injectors.

3. Where is your base timing set? The "1.5 degree/lb" may or may not be accurate. The box may be pulling more timing or less. I run without the knock sensor and with no boost retard. It's the only way it made power and that motor lasted 2 years. When we took it apart there was no evidence of detonation. The base timing is 29 degrees with the usual 3-4 degrees of "mystery timing" so the total is 32-33 degrees. It makes a ton less power with 28 degrees (~30rwhp loss).

Fix your fuel probelms. Once it's fat enough, you need to set the base timing to a reasonable point, maybe 28 degrees, and start backing off the boost retard. If you are seeing knock retard, you need to turn off the knock sensor for testing.

Do this stuff and report back. But all you have learned so far is that you need more fuel and that it isn't safe to test it at any higher rpm until that's fixed.

Rich Krause

 

It definitely looks like you are not close to your potential at all. I agree with Rich. And I think once things are dialed in and you reach your actual maximum power, you'll be really suprised and happy.

If you already have the superfueler then difinitely don't get the impedance box. Once your timing and fuel is controlled properly to allow you to actually see your max power maybe at 6200rpm, you will see a lot more power.

good luck

 

I just dont understand why so much injector for a given HP!!! it just doesn't add up...

with 3 92lb'ers and 8 50s and a BFSC you should be able to do 766 rwhp... if you are close to maxing out your injectors (80%) then your BSFC is about 0.74???????

THat doesn't seem right and I am on the same track as you are...

I finally found some 50lb'ers and I will be installing them next week or this weekend, depending on WHEN i receive them...

The thing is that my total advance is 35 with the mystery advance included and I have set at 1.5º/psi... which means that at 9psi and 5000rpm I am getting 13.5 retard that is about 22º of advance... I was thinking what if I lower my boost and remove retard, could it yield in more power and less IAT?.. I will try and see if adding race gas makes any difference, which it should.. a ton.. lowering .5º/psi of boost i gained 18rwhp from down low!!!

The fuel problems will be addressed. I just dont get why I am getting a fuel problem with the available injectors, when the fuel pressure is at 70psi at WOT and 60psi normal...

with the 30s and 3 96's I should be able to do 583 rwhp... unless the fuel from the superfueler is not as "important" or equivalent to the port injected one...

I am getting a 0.91bsfc since I am maxing out my injectors??????? THAT doesnt sound right!!! I changed my coil today.. I hope it helps in some way.. I am getting 8mpg city and 12mpg highway..

Honestly.. dont know.. and dont understand.. is it my O2s?? they are new OEM GM... but they occilate properly part throttle...

Any help would be nice.. thanks

 

Highlander: these motors are fuel inefficient with a centrifugal SC. Don't forget, those rough fuel injector size formulas don't account for conversion of engine to rwhp. For 600rwhp, add 15% to convert to engine hp and you get ~700hp. Using a BSFC of 0.65 for 700hp and an 80% duty cycle gives ~570lb/h of fuel. So, you need more injector.

BTW: my BSFC with an AF ratio of 12.3:1 at peak power is 0.65, that's where I got the number.

Rich Krause

 

Well.. using .65 I need more injector for my aim at 520rwhp...

I will install the 50s and see how it goes...

 

On Allen's 95Z (www.caspeed.com) with a 383 S-trim no aftercooler with the MSD 50#/hr injectors at fuel pressure of 50psi, he saw 510rwhp with injector duty cycle around 80%. So you should be fine with the 50#/hr and three 92#/hr injectors for your superfueler. Once your fuel is taken care of, you can work on your timing better.

good luck

--Hugh

 

Thanks man...

I hope I get them tommorrow.. I will sure know tommorrow or this weekend on the dyno..