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Discussion Starter #41
With the stock turbo, there in no sense revving beyond the factory redline, because you don't make any more power. With a the FP68 turbo and 93 octane you can run at least 25psi to 8000rpm, but I would not go over 7200 myself with factory internals. Forces on the rods increase with the square of rpm. At some point the valves will float. The cost to run 8000rpm safely is high.
 

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Yes, running any eco over 7500rpm with the stock balance shafts and valve springs in place is asking for trouble.
 

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I would not go over 7200 myself with factory internals. Forces on the rods increase with the square of rpm. At some point the valves will float. The cost to run 8000rpm safely is high.

I wonder what the valve float RPM is? Setting spring tensions is always a compromise between longevity and effectiveness. Fit some real bear traps in there and the valves won't bounce, but you wear out the valve gear much more quickly.

And valve springs do lose tension over time, and it makes one nervous knowing that on engines left to sit for some time, a bunch of springs are in full compression for months or even years. The stock RPM limit on the sort of old Lamborghini engines I play with is 7900 RPM, but I don't know many owners that will run them to that, as they fear the consequences of even one spring having lost enough tension to allow a valve to bounce at, say, 'only ' 7500. On an 'iinterference engine' one touch is all you get.

Even on the old MGs I race, you sometimes go through a couple of boxes of NOS springs before you get a set that are actually at or above the tension you want.

Which raises a question I should know the answer to, but don't - is the LNF an interference engine - in other words if a chain breaks, will the valves hit the pistons?
 

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Discussion Starter #45
Still no dyno data, but here's three HP Tuners' scan charts to compare the boost spool-up of the FP68 vs EVO3-16g vs stock turbo. Please don't try to read too much into the comparison regarding loads, etc since the air temps, dates, tunes etc are all different. But all three are ECM controlled boost in 3rd gear. MAP is 14.7psi+boost. The chart name refers to the turbo and date of scan. As you can see both FP68 And EVO3-16g spoolup about the same, 500rpm or so later than the stock turbo. The MAP line goes flat on the 16g & FP because the boost is higher than the ECM will output on the OBD2 port to HP Tuners.
 

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Thanks for the info Dave! Looks like that turbo spools nicely! My STi's GT35R spools nearly 1000rpm later, So the FP68HTA seems to be a very nice street turbo.

Russ
 

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Ordered my FP68HTA setup along with external BOV flanges on the pipes and an Evo 9 BOV. I'll try to document the install.

Can't wait to drop this in and feel 350+ WHP (hopefully)!
 

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Dave, what boost level are you now running?
 

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Well, if you did it, I should be able to do it too :). Do you have your full set of after market pipes and intake on your system? I do not and am wondering if I will need these supporting mods to run properly at 25psi. I have the stock airbox (with K&N panel filter) and the left (drivers side) pipe is stock with the restrictive kink. What do you think?
 

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Discussion Starter #51
Well, if you did it, I should be able to do it too :). Do you have your full set of after market pipes and intake on your system? I do not and am wondering if I will need these supporting mods to run properly at 25psi. I have the stock airbox (with K&N panel filter) and the left (drivers side) pipe is stock with the restrictive kink. What do you think?
That will help but may not be necessary. Most important is gas octane. I use 93 and an octane booster for safety when I spike to 28-30psi occasionally in testing.
 

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Having blown engines before, I am cautious in my quest for HP. 91 octane is pretty crappy octane so I have to move slow. My experience with tuning other cars is that hp is found in the dance between timing advance and boost.
 
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