I have a 93 so ive got the wonderful speed density setup and 22# injectors. Ive got Lightly ported Trickflow heads and an xfi280 cam full boltons and LT's will the stock injectors work or should I be upgrading and to what.

 

The stock injectors are fine for ALOT more hp! Search online there are calculators that will allow you to VERIFY how much hp your injectors will handle.

Also since I doubt you will listen new injectors also require the injector size to be changed in the tune!

 

They may be fine, but pushing the duty cycle on them doesn't exactly help. AFPR can help keep the duty cycle down.

 

What did the on line calculator you used predict the duty cycle will be at say 325 rwhp?

Edit: The stock 22 lbs injectors will handle >330 RWHP with an .85 duty cycle 350 RWHP at .90 duty cycle so there is plenty of margin.

 

These.
http://www.rceng.com/technical.aspx#...tor_Worksheet_
http://www.injectorrx.com/sizing.html
http://www.witchhunter.com/injectorcalc1.php4
(But seeing as all the math is the same, no surprise that it doesn't change.)

http://midnighttouring.com/fuelcon.htm
This one you can calc what an injector will make at what duty cycle. I keep 80% across them all just to allow for longer life. However if you can actually push these higher, I'd be happy to know (honestly).

Recommends 25.5# (which is what 24# SVOs are @ our PSI).

EDIT: I'm showing 299hp @ 85% and 317 @ 90% on that last link. Then again I'm using a BSFC of .5

 

The higher duty cycle is hard on the life because the injector does not have 'time' to cool. BUT injectors are hardy and when you look at the time WOT and high duty cycle.....then factor in normal driving idle etc and you will find the time they are 'driven' hard is a tiny portion....

I try to keep my duty cycle always below 95!

I have run setups over 100%, that happens sometimes in boosted setups. But even in Boosted the engine comes down in RPM and DC is less than .85 most of the time.

If you have larger injectors and can tune no reason not to change...if you are on a budget why change them before you have too? I never ee people get more than a few bucks for old set so not like you are losing money abusing the set you will someday 'throw away'

 

You guys do realize that those calculators are based on FLYWHEEL hp, not RWHP right? So given the " Find HP Value of Selected Injectors" calculation on http://www.rceng.com/technical.aspx#...cted_Injectors , then it gives a rating for 22# injectors to max at:
281.6 crank HP @ 80% duty cycle
316.8 crank HP @ 90% duty cycle
352 crank HP @ 100% duty cycle

94-97's use 24# injectors, giving max:
307 crank HP @ 80%
345 crank HP @ 90%
384 crank HP @ 100%

So, what you need to do is datalog your car at WOT to redline and see what your duty cycle is at. With heads and cam I would guess you are maxing out the injectors, maybe going lean up top.

BTW, with my stock 24# injectors with my mods (boltons, 1.7RR, heads, stock cam) I was running 103-106% duty cycle near 6000 RPM. Switched and tuned to 30# SVO's, the car now runs better than before.

 

I gather the new h/c will be going in, so the intake will be out along withthe fuel rail. Since you are already here, upgrade the injectors to 30#SVO's. Just my 2 cents.

 

Yes I agree you always collect data, BUT also you ALWAYS verify a tools accuracy.

Lets check the linked calculator on a known vehicle for sanity. The 92 Corvette which is rated at 300 RWHP and has 22 lbs injectors...

The calculator linked says 22 lbs will feed 315 hp at .5 with .95 duty cycle and 350 hp with 100 % duty cycle. According to that calculator the Vette can NEVER achieve rated hp unless it 'pools' fuel at the valve! Do you really believe GM would let a Vette out of factory with that condition? Oh wait they didn't have this calculator.

Because remember the GM Hype "...to revive the LT1 montor we needed to deliver more hp than the original LT1's 375 hp and we achieved that with the new LT1's 376 hp"

Also I have seen MANY LT1's running DC OVER 100 once tuned they had LOWER DC. WHY? Improper tune, if you do'nt have the AFR right or fuel presure correct bingo especially at upper RPM where most tunes throw fuel at the motor...

Thanks for the clarity, this will help people realize just because it is on line does NOT make it right!

 

93 Trans Am. Lt1 A4
Mods: Hooker Catback. Pacesetter Ceramic LT, ORY Walbro 255, Hypertech Thermomaster, !EGR, !AIR, And a Missing Piston

I missed the cam and hads I thought it said mild ported...and focused on signature with Cam and heads you better be making more. Now the decisionis do youchange to 94/95 or stick with your present.

Not bad to switch but decide then get tools Speed density has some good collection capability...andmany with higher hp swear by speed density...

DEFINATELY drop hypertech...

Goo luck and sorry bout missing the cam part time to update our signature

 

FIRST, I was only trying to help the guy out with the mis-information he was getting and guide him down the best path.



The factory rates engine power at the engine, NOT at the wheels. Given approximately 13% loss thru the drivetrain with an M6 with a factory rated 300 hp equals approximately 261 RWHP.


Actually using the formula from the site: http://www.rceng.com/technical.aspx#...cted_Injectors
Which is: (injector# X duty cycle)/.5 X 8 = HP rating
The math (22 x .95)/.5 X 8 = 334 hp not 315 at .95 duty cycle.
315 HP would be at .90 duty cycle.

Running .95 or 1.00 duty cycle in now way remotely means that fuel will "pool" at the valve. It simply means that the injectors are maxed out.

The calculator assumes the BSFC is .5 . If GM rated the LT1 at a lower number than this, then the injector size needed decreases. Plus, the 97 SS and WS6 were rated 315 hp, which with the 24# injectors would be at .83 duty cycle. Remember the factory only included injector size needed for the stock rated HP of the LT1, which was 275 for Fbodies and 300 for Vettes.

275 HP w/22# injectors is .79 duty cycle
300 HP w/22# injectors is .86 duty cycle
315 HP w/24# injectors is .83 duty cycle

All within close range of each other.

The 1992+ LT motors were rated as follows:

1992-1996 LT1 Corvette: 300 HP
1996 LT4 Corvette (and approx 100 SS and 28 Firehawks): 330 HP
1993-1995 LT1 Fbodies: 275 HP
1996-1997 LT1 Fbodies: 285 HP
1997 SS/WS6 LT1 Fbodies: 315 HP

None of these were ever rated by GM to be 376 HP

 

Why would you go off of rear wheel horse power instead of what the motor is ACTUALLY making? The motor isn't making less because you're only putting down XXXhp to the street. So really you'd want to go off of what the motor itself is making so you don't screw up the tune. The AFR isn't going to change because you have an A4 instead of an M6.

Also, yes I knew it was FW HP that it was asking for, even though Battle said BHP. If I had put in his 325bhp, the injectors duty would've been 104.3% duty for 22#. That's assuming 325bhp = 365fw hp. Again, at .50 BSFC. At .45 the DC is 93.86%. Still too much for my liking, but that's my opinion.

 

You both know alot more than I?

A GM 350 made 375 flywheel hp in the 60's and with electronic control and 25 years you believe the LT1 an LS1 has not equalled this? Yea sure you know your stuff alright.

And you use wheel hp because most don't want to remove their engine to make the a hp measurement. Do you think the dyno you drive on measures flywheel?

And for the auto vs stick the accuracy of measurment is not within 5% so yes it is moot.


Thanks

 

I got the hypertech for 15 bucks and used it just to get the fans to kick on earlyer. But back to the thing should I pick up some injectors or turn up the Fuel pressure? Also im keeping speed density and Ive got the chip burner and crap to get it tuned.

 

My post was actually more in reply to KG, not you, but anyways... I see your point there. Why do all these calculators ask for FW HP then if the majority of people will have BHP?

 

I guess this statement tells it all. GM forgot how to make horsepower. Bad GM, Bad GM.

 

Flywheel Horsepower (FWHP) (a.k.a. Brake Horsepower or BHP)is the truest measurement of the output of the engine. There is no accurate way to measure the amount of parasitic loss through the drivetrain using just a calculator. Nor should the calculator care about that. What transmission you couple up to it, what type of differential you use, are inconsequential to the FWHP of the engine.
Rear Wheel Horsepower (RWHP) is what we use for our vehicles, because the end user (us) only cares about what we put down on the road, parasitic loss and all, so we use a chassis dyno. That gives us data on a case-by-case basis, and takes into account our entire setup, which can vary widely.

 

In order to really know if you need bigger injectors, get some log data. You will need to log some WOT at redline. You can then calculate, from the logs, what your DC is truly at. This will determine if you actually need larger injectors.

 

Well right, but like I said, I find it weird that they don't utilize BHP instead of FWHP :\

(BTW I know all the terms lol but thanks)

 

I think it was 1971 when GM switched from gross to net hp ratings