With 21 pounds of boost on 93 octane tune, should I...

[nooner]

I have a new engine installed (Aluminator) and I'm running a Whipple 2.9 with the stock 3.5" pulley pushing 21 pounds of boost. Heads are ported and have "stage 2" Comp cams. Intake is a JLT RAI with 110mm MAF housing and Accufab 100mm single blade TB. Exhaust is Kooks 1 3/4" long tubes with 3" collector and Kooks 3" o/r x-pipe which necks down to 2 1/2" into Spintech mufflers for the Roush side exhaust. The mufflers have the input and output on the same end for the side exhaust. I'm pretty sure the restriction of the mufflers and side exhaust is why boost is so high with the stock 3.5" pulley. My mechanic and tuner say I have two options given that the side exhaust stays and we are tuning for 93 octane pump gas. Either we can stay with the 3.5" pulley and 21 pounds of boost and pull timing on the tune to stay safe, or back boost down with a 3.75" pulley.

According to superchargersonline.com and gettorq.com which carry the 3.75" pulley, they say it won't fit under the stock hood without a k-member spacer kit. The pulley should only be 1/8" higher than the stock pulley. Is clearance really that tight? If so can the hood be ground out a little to provide an extra 1/8" clearance? The side exhaust and stock hood stays so I need to find a solution that keeps these. Yes, I know there is a lot more potential power there if I go with a better fuel, better exhaust, and/or more boost, but at this level I have more than enough power.

What should I do? Keep the 3.5" pulley and pull timing? ...or drop boost by switching to a 3.75" pulley? ...or something else?

 

[mach1033]

Is Torco an option?

 

[ugotbit03]

3.75 or a 4.0 should clear the stock hood. I know for a fact 03steve is running a 4.0 RR on a 2.3 without issues.

The 2.9 has the same case height as a 2.3 and the snout and pulley are in the same location.

 

[nooner]

Is Torco an option?

Its an option I don't really want to use.

3.75 or a 4.0 should clear the stock hood. I know for a fact 03steve is running a 4.0 RR on a 2.3 without issues.

The 2.9 has the same case height as a 2.3 and the snout and pulley are in the same location.

That's good to hear. I really don't know how much clearance is there but I didn't think an 1/8" or 1/4" would make much difference. So you are sure he is not using a k-member spacer kit?


Does anyone know if I would be able to get similar power levels with either setup? ...or would one solution be safer than the other?

 

[ugotbit03]

No K-member spacer.

Personally, 16-19PSI on stock compression is where I would want to be on pump gas.

 

[nooner]

No K-member spacer.

Personally, 16-19PSI on stock compression is where I would want to be on pump gas.

Good, another opinion for no k-member spacer.

As for dropping back to 19 PSI or less, I agree, since that's pretty much what I've read on these forums. But I don't have enough knowledge to say why though. By pulling timing at higher boost, I believe it can be made just as safe, but does that mean it will have less power? If so, then that would be why I would want to back down the boost, right? So we can dial in more timing to increase power?

Right now on the break-in tune running 14 degrees of timing, and cutting the pull short at 5800, we are at 560 whp and 521 tq. Torque was very flat and peaking at about 5500 and power was still climbing fast at 5800. The tuner thinks it would be around 620 whp at about 7000 rpms on this tune. I'm not sure how much more timing he would dial in on the final tune at 21 psi.

 

[johnjon87]

Personally, 16-19PSI on stock compression is where I would want to be on pump gas.[/QUOTE] +1

Is Torco an option?

IMO being at more than 19PSI Torco is a must! I feel like your playing with fire at 93 oct and that psi..

Only other suggestion would be move to E85..

 

[mach1033]

Personally, 16-19PSI on stock compression is where I would want to be on pump gas.

+1


IMO being at more than 19PSI Torco is a must! I feel like your playing with fire at 93 oct and that psi..

Only other suggestion would be move to E85..[/QUOTE]

I dont know why guys are afraid of torco. I ran it for 2 years without issue. Not saying the OP is afraid but it seems a lot are.

 

[fangs99]

Meth?

 

[Blueline]

I cant believe your making that much boost with the 3.5 pulley. Im running a 3.5 pulley on my 2.9. No porting in the heads, stock manifolds, o/r x and borla stingers. I peaked PSI at 18.8 around 6800 rpm. I run a bottle of Torco per fill up, (93 octane) just for added insurance. I dont see how you can be making so much boost with ported heads, 1 3/4" longtubes etc.

 

[nooner]

I dont know why guys are afraid of torco. I ran it for 2 years without issue. Not saying the OP is afraid but it seems a lot are.

And I'm not afarid of Torco, I simply just don't want to bother with it. My ideal solution would be to determine what is causing the restriction and reduce it so boost gets reduced.

Here's how I see it. Increased boost equals increased power and increased chance of detonation. Increased timing equals increased power and increased chance of detonation. So if you increase boost you have to cut back timing to decrease chance of detonation. If you decrease boost you can dial in more timing for more power.

There in lies my question... does more boost and less timing (so its safe) produce as much power as less boost and more timing?

 

[nooner]

Meth?

I like this option better than Torco.

 

[mach1033]

I like this option better than Torco.

Why would you like Meth better than Torco?

 

[nooner]

I cant believe your making that much boost with the 3.5 pulley. Im running a 3.5 pulley on my 2.9. No porting in the heads, stock manifolds, o/r x and borla stingers. I peaked PSI at 18.8 around 6800 rpm. I run a bottle of Torco per fill up, (93 octane) just for added insurance. I dont see how you can be making so much boost with ported heads, 1 3/4" longtubes etc.

I have heard the Roush side exhaust were restrictive but I didn't think it was THAT restrictive. But it does seem to bear out since with stock pullies I was pushing a little over 9 PSI.

In the coming days I hope to be able to determine if the restriction is the side exhaust, and if so, how much is the mufflers, and how much is the 120 degree bend coming out of the mufflers to the side. Spintech makes the same mufflers with 3" inlet/outlet and I can switch to an oval pipe out to the side that is equivalent to a 3" pipe, but the exhaust tips are not available in any other size so I'm not sure if upgrading the mufflers and outlet pipe would help.

 

[cobracide]

eh 19# max on 93 octane.

 

[nooner]

Why would you like Meth better than Torco?

Because blending Torco is less precise than spraying meth. Neither is an option I want to use though. But thanks for the suggestions. They would certainly be considered options if the most power was my goal.

 

[nooner]

eh 19# max on 93 octane.

So everyone says. But no one says you can't pull timing on 21# boost to make it safe.

 

[cobracide]

So everyone says. But no one says you can't pull timing on 21# boost to make it safe.

Let me ask you this - What would you RATHER do? Pull timing or lower boost? Most run better with more timing and less boost than the other way around.

 

[nooner]

Let me ask you this - What would you RATHER do? Pull timing or lower boost? Most run better with more timing and less boost than the other way around.

I don't know. That's the kind of answer I'm looking for. When you say "runs better", what do you mean? ...More power? ...safer? Just exactly what does that mean? Forgive me, but I really don't know.

 

[cobracide]

To maximize your performance, OCTANE should set your timing limits. 21# is too much for a reasonable timing 17-21* with a Whipple. I hope the "drop the boost" vote wins.