BrainDrain_dx

I'm trying to get Magnuson reliabilty out of an ati. I have a 2000 vert with 14K miles on in. I purchased a ati with single intercooler from A and A along with upgraded idler pulley bracket and a racetronics fuel pump. I went with a 4.10" pulley (comes with 3.85" standard) since I'm shooting for 450 RWHP. Is that resonable or will it be lower?
I have seen ati's put out from 400 to 500 on seemingly stock engines as this point I dont know what to expect. I can not find any kind of chart and what pulley corresponds to boost pounds, like a 3.85 makes 7#, a 4.10 makes 6# and so on so I can make an educated gues. Does anyone know and are there sizes inbetween?
Is it better to run a smaller (boost) pulley with a semi aggressive tune or a larger (boost) pulley with a conservative tune to achieve the ~same horsepower.
I'm going to have the car tuned on a dyno but dont want to have to do it twice if I choose the wrong one.

My current thinking is - stock kit with 3.85" on a stock engine makes ~450 RWHP, I change to a smaller pulley with 1# less boost to get ~420 then add the single intercooler and get less pressure drop and the upgraded idlers to eliminate slip and I'm right back at 450 where I want to be.
Any guesses before I start installing this mess in two weeks? :banghead:
Car is a six speed, engine is completely stock and I only care about rear wheel horsepower numbers.


[Modified by BrainDrain_dx, 6:32 AM 7/22/2003]

BlownZ06

If you have got a stock bottom end go conservative! - 4.10 or larger pulley, AFR of 11.7 to 12.0, max 7# boost. If you go more than 7# boost keep $3-4K handy for a forged bottom end, you will need it very soon. Many have tried and we all have new engines now!

BrainDrain_dx

I cant go larger than 4.10 due to the upgraded idler bracket but I have no idea how much boost that will make. Especially with the single intercooler thrown into the mix.

BlownZ06

I've got the same setup from A&A that you have but now I have the forged bottom end. The point I'm trying to make is keep it conservative. Your car will be unbelievably fast, try not to get fixated on the big HP#, experience speaking again.

blu00rdstr

I second that. Don't run without a boost gauge, we don't know what the SIC upgrade does. I was running at a tuner reported 8# with a 3.85" and no boost gauge, then did the A&A setup/MMS tune and broke a piston and subsequently cracked the cylinder sleeve. Car is up on jacks, I pulled the motor on Sunday.

:cry :cry


[Modified by blu00rdstr, 12:21 AM 7/22/2003]

SleepieAce

I'm running the regular twin intercooled setup at 7# and getting right at 450rwhp when it was checked. I'm installing LT headers and complete exhaust in the next three weeks and plan on taking it back to the dyno afterward just to find out the difference. The engine is stock other than the ATI so far.

I think from what I've read that the setup you're suggesting (single intercooled 6# pulley) will probably give you what you want, but I would definitely suggest a boost gauge. It seems that everyone so far who has pushed over 7# on an ATI has eventually had to install a forged bottom end. So far I haven't heard from anybody who can definitely say how much the single intercooler ups the boost. Just my .02 and good luck with the install :cheers:

BrainDrain_dx

I bought boost and fuel pressure gauges and they are installed already. Im not interested in max power, I have set the limit at 450. What size is the 6# pulley - is that the 4.10"? :confused:

BlownZ06

I don't believe there is a difinative answer to pulley size and amount of boost due to all the variables, i.e who's bracket assembly your using, single intercooler vs. twin intercooler, compression ratio, belt slippage, headers, cats, exhaust.

4.10" should be a good starting point, just have your tuner watch the boost guage on the dyno and tell him not to exceed 7#.

Shinobi'sZ

Its amazing what you can learn through blowing up your motor,,,,whether you are doing your own repairs or paying somebody else to do them. I agree with the above...it is a good feeling to have forged internals...people should not get a false security that they can not damage a Forged Internal motor...it can take more abuse but is not indestructable.

xtream1

Great, now you tell me... :( and here I thought I would be OK with a million pounds of boost. Care to guestimate on the limit? I bet jim hall would know the limit. :D

jeffh355

Andy built my forged bottom end and we're running 12+ lb's on it. Without the lower end I would think 6/7 is as far as you want to go.

BrainDrain_dx

So its all about boost not horsepower to some extent. On an LS1 I can run 7 PSI and/or make up to 550 rwhp. If I run 8PSI and make 400hp my engine will pop and if I run 5 PSI and get 600hp my engine will still pop.
So then I can conclude that I should run 6 PSI and get my base HP - say 420 to 450. At that point the reliable thing to do is change out a cam or headers to get more hp instead of jumping up to 7 psi. Pulley selection doesnt matter as long as it makes the required boost but noone really knows what size will do it with a single intercooler setup...


[Modified by BrainDrain_dx, 12:16 PM 7/23/2003]

blu00rdstr

Welcome to the grand experiment!

Rules of thumb to my best recollection:
<li> Stock pistons good to 7lbs boost
<li> Stock pistons good to 550HP
<li> Stock crank good to 700HP :eek:
<li> Stock runflats good to 350rwHP
<li> Stock Z06 tires good to 450rwHP
<li> Stock ATI pulley setup good to 9lbs boost
<li> Drivers license good for 6points

xtream1

:iagree: We've got to do something about this! Blown vettes should at least be allowed 12 points....it's only right. :blueangel:

SleepieAce

:iagree: :yesnod: This goes along with all the research I've done so far. Amazing how strong the crank is :thumbs:

And as far as the license goes :lolg: :lolg: :lolg: Blower cars should get a few more IMHO :auto:

BrainDrain_dx

Are the numbers for the pistons and crank NA numbers? I know that if Im putting out 700 RWHP with an ATI its putting alot more load on the engine.

I have a sportbike to lose my license with! Now your telling me the car will take it too :rolleyes:

blu00rdstr

Somewhere (I think it used to be here ) I saw that it took about 50hp to drive the ATI, each model had a different rating. So your engine may be putting out more power than is measured at the wheels, making it closer to the edge than you think.

blu00rdstr

Actually I did the :eek: because I realized I was already at 522rwHP which is 652fwHP. Adding heads/cam should bring up HP over 700 at the flywheel, with the stock crank...


[Modified by blu00rdstr, 1:39 PM 7/24/2003]

BrainDrain_dx

alright so then if the stock pistons are good for 550 fwhp... not rwhp, then I take that minus the 50 for the supercharger minus the 15% my drivetrain eats I get 425rwhp. anything over that and my pistons take a flop.

:eek: ack that dont seem right. Is it maybe 550 rwhp or 630 fwhp. Now I drop the 50 for the blower - and take out the drivetrain loss to get 493rwhp

either way anything over 450 is pushing it unless the blower isnt robbing that much hp

Should have bought a turbo :cry

xtream1

700 hp installed on a 6speed (has approx 15% drivetrain loss) tranlsates to approx 600rwhp. On an automatic it's approx 20% loss. So, given a projected 600rwhp goal, an automatic is right at the expected limits of the crank capacity. What a thought :eek: Although to date no cranks ahve been roepoted broken.