Hahn Kits - What octane - High Boost enlightenment

oldskool · 08-22-2008, 01:05 PM

If you look at the page on HRC's site with the Stage 2-4 dyno graphs, you'll see that stage 3 is quoted as a mix of 100 and 91 octane, but stage 4 is quoted as pump gas. The highest numbers do not state what fuel is used.

So what does it take to achieve the 373whp on stage 4 as the "soul-food solstice" did? Is it only possible on race fuel or are all these numbers doable on 93 octane? Is there a whp limit on the 2.4 w/ stock compression?

Also, I cannot find details on the "high boost" option. I've read that its a valvetrain (dual coil springs) upgrade and thicker head gasket, which would lower compression slightly. Is this why stage 4 is operable in pump gas?

Fow what its worth, I know it would be easiest to just call up HRC, but I like to hear from end users/ those with real world experience. If ECOBOOST chimes in, thats cool too

nighttripper · 08-22-2008, 03:55 PM

ClearBraInstall · 08-22-2008, 05:34 PM

Ok,

Now that I own the Soul Food Solstice, I can tell you real world experience with the car. First the car only has half of the high boost option which is the valve spring upgrade. I have yet to lower the compression with the head gasket kit. I can tell you that 93 octane is only going to net you about 12 to 13lbs of boost. Which would probably translate to about 300whp. As you mix in a little race gas, say 100 octane, you can increase the boost as follows.

93 Octane only = 13psi boost
93/100 mix (50/50 ratio) = 15 to 16 psi boost estimated 340whp
pure 100 race gas = up to 20psi boost and the 380whp. I know that they have converted a Sky to the full High Boost kit and lowered compression and they were able to get 330whp on 93 octane fuel.

One thing important to watch is spark retard. If you have a dashhawk, you can easily monitor this vital information. This is how much timing is pulled due to detonation. The car should only see about 2 to 3 degrees of spark retard under WOT conditions. Any more and you need to increase octane or lower boost. I have this setup on my dashhawk and monitor it like I monitor engine temp. Listening for audible knock is not good enough, normally you don't even hear audible knock till about 7 or 8 degrees of timing pulled and then its too late. All it takes is one bad knock and your engine is toast. So those that pay close attention to this will get many happy miles out of their boosted cars.

As far as longevity, I can only say that my car probably has had the most punishment with the track time that Bill Hahn put on it as well as my regular Autocross racing. The car now has 20K miles on it and is still going strong. I don't always run 20psi boost, I normally run the car around 15 psi.

Hope this answers your questions. As always I am sure you can call Hahn and get the info on the High Boost kit. I might just be doing that mod myself soon.

Clear

oldskool · 08-22-2008, 09:19 PM

so the bottom line is stock compression = max 300whp on pump gas. your figures are in-line with those on the HRC website - indeed i think some of them are from your car

I've searched long and hard and i just dont have a convenient nearby source or race fuel (100+ unleaded)

so with the thicker head gasket/lower compression, what kind of numbers are possible on pump gas? Can I get 380whp with the stock pistons and 93 octane?

ClearBraInstall · 08-22-2008, 09:58 PM

Quote:

Originally Posted by oldskool

so the bottom line is stock compression = max 300whp on pump gas. your figures are in-line with those on the HRC website - indeed i think some of them are from your car

I've searched long and hard and i just dont have a convenient nearby source or race fuel (100+ unleaded)

so with the thicker head gasket/lower compression, what kind of numbers are possible on pump gas? Can I get 380whp with the stock pistons and 93 octane?

Bottom line is you will only be able to get 330whp on 93 with the high boost option. Might be able to achieve the full 380whp with water/meth injection on 93 octane.

Clear

nighttripper · 08-23-2008, 07:51 AM

Is the high boost option available only with the Stage 4 kit?

oldskool · 08-24-2008, 08:12 AM

Quote:

Originally Posted by nighttripper

Is the high boost option available only with the Stage 4 kit?

I think thats a yes.

I wonder why hahn's site doesn't specifically state that the high numbers (380whp) require race fuel? Also, I'm sure if Hahn maxxes the stock compression engine at ~300whp, no one else is going to do much better.

Don't get me wrong though - 300whp in a 10.4:1 compression roadster that weighs ~2900lbs is sure to be one fun ride.

nighttripper · 08-24-2008, 08:00 PM

I'm not sure that I would need more than that(300 hp) but I'm thinking on how to make it more durable on the engine. I think if the high boost option were available on stage 3 you could up the boost abit so that it would be around three hundred without the race gas... but I could be wrong I'm no expert, as I have told Bill.

oldskool · 08-25-2008, 11:21 AM

I'm sure you could work something out with HRC - they seem to be very flexible as far as customer requests. If its reliability your concerned about, I'd say this is one company that's done its homework and can attest to reliabilty at a given power level.

My main concerns were what is the maximum power level achievable on 91-93 octane. As I said, I do not have a convenient source of race fuel, so any numbers put down on high ocane are pretty much just for company bragging rights to me. Its nice to know what the bottom end is capable of, but I'd need lower comp. pistons for those boost levels i guess.