Need Boost Advice with 91 Octane, 8.5:1 & AFR225 Heads
02-11-2008, 09:03 PM
#21
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Well, there has to be some rule of thumb out there that with X Octane, and Y Compression ratio you shoul dbe able to run Z boost... Is there not such a thing?
Also do Turbos really do not have any parasitic losses? like superchargers do?
Also do Turbos really do not have any parasitic losses? like superchargers do?
02-11-2008, 10:59 PM
#22
No one route is perfect.
Certain things make power, boost first, timing second, compression last. You need to figure out how much boost you want, then how much timing you feel you want to run, then you will find out how much compression you can have.
Rick
02-11-2008, 11:07 PM
#24
02-11-2008, 11:38 PM
#26
We all have to learn the same way. Trial and error. Those who taught me made me try as well. Its good for you.
About 8.9 to 9.1 seems to be a sweet spot with these motors. And without giving it all away, you can run a good amount of timing with a good amount of boost at that level. I run about 18psi on the dyno at a max of 16-18* of timing on 91 and meth. Thats pretty good. I only have about 9.5 to 1 compression. Now, if I dropped it down some, I could possibly run the rest of the timing to make up for the size of the camshaft. Hard to say. Or I do the right thing and size mycamshaft down to come on stronger. I have a bigger than I like sized camshaft. So I play the game of "power band" or "power in the power band". Its a matter of all of it. Timing is cylinder pressure as well. The more you run, the higher the cylinder pressure becomes. So, if your camshaft needs more timing to become affective because it happens to be on the bigger side of things, then you need some more room to make up for the timing you will need. This is where all the balance act of octane, timing, and what you can get away with comes in to play. Sorry, no Chart.
Rick
03-16-2008, 10:04 AM
#27
I just caught this thread, what a great build!
In general, what I've always been told/read/heard is the point of running lower CR is to allow you to run more boost and/or timing without detonating at a certain Octane Rating.
Seems like fairly recently we are able to run higher compression with PDB, however I think this has more to do with the size of the HU (i.e. HU's only capable of XX lbs of boost so there was actually a tolerance to add CR) and of course, the better efficiencies of today's PDB.
Parish has a solid approach this, he is able to make a ton of power with his method of attack
In general, what I've always been told/read/heard is the point of running lower CR is to allow you to run more boost and/or timing without detonating at a certain Octane Rating.
Seems like fairly recently we are able to run higher compression with PDB, however I think this has more to do with the size of the HU (i.e. HU's only capable of XX lbs of boost so there was actually a tolerance to add CR) and of course, the better efficiencies of today's PDB.
Parish has a solid approach this, he is able to make a ton of power with his method of attack
03-16-2008, 10:42 AM
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Well Project is finally done, after 7 months. I will post some pictures soon. Running the Whipple at 12 psi and 12deg of timing until the engine breaks in. Then will go up to 15 psi and 9deg. Will have Meth injection from Snow Perf. installed with an on-demand switch for days when its over 100deg which we get it socal in summer time.
The car hauls A** and the 4L80 is much much better. Had to go through two trannys and two Torque converters. The first tranny, I was chated and felt like a sucker. It was an old standard 4L80 sold to me by speed Engineering. He had sourced it form somwhere else. Cost me $5K, had about 200K miles on it and the wrong output shaft. The first torque converter from RPM Transmissions with 3 clutches, had too high of a stall, 2400. I hate stall converters. So had another one built with 1800 stall and 5 clutches I must admit, I like stock factory converters better, but they are not strong enoung.
The new 4L80 from RPM is MUCH MUCH better. I am happy with it now, but do miss the taller 4L65 4th gear. I may go down to 342 rear from 373s, just need to lower the RPM on the freeway. Turning 2500RPM at 75mph. Its about 500RPM higher than the 4L65.
The 4L80 needs more cooling than the 4L65, but the torque converter has a lot to do it. So two B&M external coolers are ordered. Still need to come up with a cold air intake and swap the battery location.
I must say Andy at A & A Corvette, is an amazing guy. This man knows what he is doing. He is not done until its done right.
I have not floored the car yet. But just getting on it softly here and there and while cruizing is more than even my Eibach suspension can handle. I thought I had enough suspension, but for this much power, I will need more, hope I can find something adjustable.
running 60lb injectors, and the oil presssure is 60psi. The Ron Davis Radiator with a 160 thermostat keeps things pretty cool for the motor which helps keep detonation at bay.
Gas mileage dropped from 14MPG to 10MPG. The motor is now 1000cc bigger, and the tranny has more parasitic loss (4L80) and the 3.3L whipple takes more HP than the 1.8L Magnuson.
By the way I will have the other torque converter for sale. LS7 to 4L80 $600, paid $1000, drove for 5 miles
Will update you with pictures....
Escalade ESV 2006 AWD
Built 4L80 conversion with Billet output shaft and shift kit - deep pan RPM Transmissions
Torque converter with 5 clutches - RPM transmission
upgraded HD AWD transfer case from SS4
Custom made drive shafts
427 cuin, Aluminum Block
8.5:1 ceramic coated pistons
60lb injectors
72cc AFR Heads
Lunati Crank
Eagle rods
6100 RPM shift Point
3.3L Whipple Supercharger with 10 rib pulley set 12psi - Max Limit 25psi
60lb injectors
Large Ron Davis Capacity Radiator
Large Capacity Intercooler from Ron Davis
long Headers - REMOVED --- went with shorties and kept stock Y tubes
High flow Cats - REMOVED
Corsa Touring Exhaust - REMOVED Way too loud. Stock exhaust is good enough
Brembo 8 Piston calipers Front & 4 piston Calipers Rear
Eibach Suspension all around 2/1 drop with HD stablizer bars
Widened rims (20x11) 325/50VR20 TOYOs
