TKO500

iTrader: (5)

Hey guys,
I am thinking about dropping a supercharger in my Z28. When I built the motor I intended only to run it normally aspirated. However, a buddy of mine just bought a fox body with a 9psi charger on it and I like it, but it will also smoke my car

So my motor is a fresh 350 (9.6 or 9.8:1) with under 200 miles on it. Edelbrock TPI runners and lower intake, 58mm thorttle body, 24lb/hr injectors, afpr, Trickflow Kenny D 195 heads, LT4 Hot Cam, 1.6rr's, headers, high flow cat, 3" exhaust.

What can I safely get away with running for a charger, if anything without lifting the head gaskets right out of the motor? With the money I have in the motor and tranny (TKO500) I do not want to grenade the motor... yet!

Right away I am pretty sure I will need to run larger injectors as well. Any other suggestions?

Thanks!

MrDude_1

you're going to need to up the injectors of course, but 9.6 is low compression for an alum head motor anyway.. and the LT4 cam is tiny...so you're probly fine.. toss some boost at it and have fun.

84z28350

Your in the upper limits of compression for running boost. You will have to keep the boost down if your just going to run pump gas.

with 9.5:1 static CR with forced induction @ 4psi will get you an effective CR of 12:1 which is pretty much the max for 92 octane.

You may want to look into getting a set of bigger dished pistons or larger chamber heads to drop you into the 8:1 or maybe 7:1 area.

MrDude_1

lol, if it was that simple and accurate, then pumpgas LS1s would be running 15:1 to 17:1 non-intercooled boost...

really though, i think he'll be fine for low boost. id run an intercooler of course, but hes fine either way.

calebzman

iTrader: (3)

Did you improve any of your internal engine components? I agree with 84z28350. With the compression ratio you have now, 3 or 4psi is probably your max. If you're serious about going turbo, and you have stock internals, I would upgrade to forged pistons while lowering the compression ratio at the same time.

fb305svs

unfortunately, that compression is pretty high for boost... you do have alum heads, so that gives you a lot of lead way, but to run 6lbs, your going to be pulling a lot of timing out to keep it alive...

what type of componants were put in the motor? any forged pieces?

Naft

that compression ratio under boost chart is complete posh. you cant calculate how the static c/r vs boost pressure will affect things without complicated partial differential equations with more variables than just c/r and boost psi. bottom line is that a properly sized turbo or supercharger is much more effiecient at compressing air than your engine, which is a major reason why supercharging works. if this werent true, you would get almost the same amount of power by raising compression from 9.5:1 to 12:1 as you would from adding enough boost to get to 12:1. you dont. the chart is given on the safe side of a gigantic margin of error(definitely over 30%) so people dont blow up their engines and get mad.

the bottom line is that it will totally depend on your chamber design, piston shape, quench, cam, how well your exhaust flows, how hot your engine runs, how efficient your compressor and intercooler are, block and head material, head gasket thickness, etc. i know of a guy running 15 psi with a turbo on a stock 3.4 v6 bottom end and iron heads at 9:1 compression. not just 15 psi but 336/397 at the wheels(engine made 160/200 at the crank stock), he isnt pulling timing to get high boost #s. according to that chart thats an effective compression ratio of 18:1. on pump gas with iron heads & block.

bottom line: you can put more than 4 psi in that thing. how much, i dont know, but you will be fine slapping on 6 psi, with a good intercooling setup and proper everything else 8 or more should be doable on pump gas. and thats a conservative estimate.

the only time i would even consider that chart is with old highly inefficient(like under 50% adiabatic efficiency) roots blowers with no intercooling and mechanical advane distributors. with computer tuning, a modern turbo setup, suffiecient intercooling, and electronic timing with knock sensors and all that gab, forget about it.

JohnBlazeLTZ

The good thing about running a blower on an engine with more compression is that the engine doesn't have to work so hard to achieve the desired hp/tq numbers. things can also be balenced out with an overbore...355...357...the larger the cubes the more difficult the tune though...

ZEEYAA

Hey TKO, you already have a good combo, just spray his A$$.....lol.

ineeedmorespeed

I bought an '89 Z28 from a kid who apparently built the following truck block with his shop instructor.

350 c.i. 1 piece seal truck block
New .030 forged federal mougal pistons. Approx compression is 9.9 : 1
Block and Crank were magged.

New Crane Hyd Flat Tappet Cam, .450 lift, 238 dur.
New Crane springs, keepers, retainers, pushrods, and double roller timing set.
New Proform 1.5 ratio roller rockers.

New melling high volume oilpump
New high volume water pump
New chrome oil pan and timing cover

Vortec "Ramp" style Heads
Ported and Polished. 5 angle valve job.

TPI is still stock parts

I've taken it to a mechanic to verify most everything but do you think the est compression is accurate? Is it easy/inexpensive to check the compression? If it is accurate...is nos my only option? thanks in advance...

ineeedmorespeed

bump

TKO500

iTrader: (5)

Thanks for the compliments! I am in the process of pulling the car apart now to move onto another project.

TKO500

iTrader: (5)

Thanks for the compliments! I am in the process of pulling the car apart now to move onto another project.