Don&Kelly

This past year I switched the engine in my '81 coupe and got rid of the old 190 hp (at the crank) engine & put in a 350 with all sorts of goody's including Holly Tuned Port Injection - Acell - Electronic Control Module.
In the car it came out of this engine made 325 hp at the rear wheels, we've had a heck of a time finding someone to program the computer & although it runs well, it's slow .. I dyno'd yesterday and it has 207 hp at the rear wheels with 330 pounds of torque .. I know the problem is the computer .. I'm thinking of going back to a Edelbrock intake & a good 4 barrel carb .. what do you think??

:mad :confused:


[Modified by Don&Kelly, 4:14 PM 8/27/2003]

mrvette

Don, I REALLY hate to hear that, but not being familiar with any aftermarket DPFI systems and such, I don't know what to say......

BUT the principles of operation of SPFI in general....meaning by the numbers a factory oriented design...make any carb look sick by comparison....

throttle response, fuel economy..with 16-18 gallon tanks this DOES matter....unless it's a garage queen...., and the ease of starting and running in all weather patterns....

I dunno what problems you are facing, but the overall operational charactoristics of a PROPER RUNNING DPFI are so far superior to any carb....
once you have taken the plunge...I can't imagine going back...even if that means a more stock type computer, or whatever....

sorry to hear of such lousey aftermarket support...seems someone out here should know something....

GENE :blueangel:

MotorHead

Did you see it make 325 RWHP ?

I have always liked carburetors, can't gt my home computer to work properly let alone one in a car :lol:

Fevre

How do you know it made 325 out of the old car? Would be curious to see your specs for cam and exhaust. If it is running well then I am unsure whether a carb would offer better performance. I agree with Gene, once you get it tuned it is a better over all system then a carb, not faster just over all better.

LAvetteman

:iagree:

Many wish they had Fuel Injection instead of carbs. Will you be giving away the FI system? :)

e3pres

I'll trade you an Edelbrock Performer aluminum intake and an almost brand new Q-Jet for the TPI setup.

A C

Well, it will probably be easier to actually see peak HP with the carb if you are used to working on them. Everything else will suffer though, most likely. Driveability, cold starting, and gas mileage. Also, you will be out some major bucks for the FI setup, which would REALLY suck if you put on the carb setup and determine the motor is actually the cause for the low HP numbers. I am with the other guys...did you actually see this 325 RWHP pull?

PatsLs1vette

i wouldnt go back either,unless its for an all out 1/4 mile car.I just swapped injectors(24lb motorsports) in mine and now my new custom chip works even better then before.

Don&Kelly

Well you're all correct, I did not see the 325 hp pull ... but surely he would not misslead me just to sell an engine :smash: - seriously, I know that almost everyone fudges their HP #'s, but not usuall by this much ... but following your advise, I've found a Tuner in my area, & he says that I'm running "pig fat" and so that should help some .. (but not 120 horses) .. so I think I'll let him have a shot at tuning it & then see what to do. Thanks for your help ...

:seeya :cheers:


[Modified by Don&Kelly, 12:17 PM 8/28/2003]

Alwyn678

I think you should keep it and get the motor modded a bit

Puppe

I sure like to see the inside of your engine. If it´s a stock C4 vette TPI 350 it outputs a max hp of ~310 with those parts you´ve listed and then it has to be very fine tuned. If you wan´t more out of it you have to open it up and start putting down some serious work on it (heads, pistons, blueprinting and more).
I don´t have the figures on a Vette, but a normal front engine rear wheel drive automatic will loose about 30% hp on the drivetrain.
Ex. Engine 300hp * 70% is about 210hp at the rear wheels.
So calculated like this you should have almost 300hp in the engine.
I had a C4 350TPI in my Camaro and I did as much as I could without opening it up and I got 218hp at the rear wheels.
So I´m just wondering was it really 325hp at the wheels or was it 325hp at the crankshaft with some selling horsepowers too.
If it really had 325hp at the wheels, it´s possible to loose atleast 50% if your computer is badly programmed.
So lets hope it´s only the computer that needs a good programmer. :thumbs:
If you´ve gone TPI you should never :nono: go back only improve it.

Don&Kelly

I've always heard that the calculations are a 20% loss with a auto & a 15% loss with a 6 speed.

207 hp divided by .80 = 260 hp at the crank and yes I might be able to pick up some more hp with the proper tune job ... at least that's what I'm hoping .. so I might get close to 300 hp at the crank .. but that still isn't what he told me & I might consider a cam or heads to add alittle more ... it all depends on whether the turner can make a difference ..

:cheers: :seeya


[Modified by Don&Kelly, 1:44 PM 8/28/2003]

SuprJames

I spent about two months trying to get my Accel DFI system tuned to the max. After my dad and I spent hours reading books and magazines we came to the conclusion that without a dyno it was nearly impossible to tune. I was running 13.03 1/4 before I took it to one of Accel's DFI guys (EMIC) with a dyno. When he first tested it I was running around 260 HP and 310 ft lb. of torque at the rears. After an hour of tuning he got it to 290 HP and 390 ft. lb. of torque!! My mileage stayed at 20+ mpg on the highway. I wrecked the car the day after he tuned it in April so I never got to try it out at the track :( . I think I could squeeze a few more horses out with a cold air system and a radiator that actually keeps the engine below 200 degrees.

Anyway, the moral of the story is to take it to an Accel EMIC (find them on Accel's website) with a dyno. It was theworth the $90.

Fevre

:iagree: with SuprJames, dyno tuning is the only way to go with FI. I have Accel DFI in my Formula and no way can you tune it for all out performance without know what your putting down to the road. The 02 sensor readings can give you a ballpark but once you go open loop all bets are off. I'll check that Accel website for a dyno center near me with Accel experience. :thumbs:

Puppe

[QUOTE]I've always heard that the calculations are a 20% loss with a auto & a 15% loss with a 6 speed.

That sounds right for these new highly sofisticated cars but remember that a C3 vettes drivetrain was made on the draftboard about 40years ago.
If anybody knows the right %loss for C3, could you share that info with me and everybody else who is wondering. :confused:

Don&Kelly

(quote) That sounds right for these new highly sofisticated cars but remember that a C3 vettes drivetrain was made on the draftboard about 40years ago.
If anybody knows the right %loss for C3, could you share that info with me and everybody else who is wondering (quote)

Great point, I'd like to know too ...

:seeya


[Modified by Don&Kelly, 2:18 PM 8/28/2003]

Don&Kelly

SuprJames

(quote) take it to an Accel EMIC (find them on Accel's website) with a dyno (quote)

Whats' is their web site, I searched for it but could not find it ..

:seeya

SuprJames

http://www.mrgasket.com/dfimain.html

You can also download instructions.

Fevre

www.mrgasket.com

Fevre

The link to the dyno centers is not working right now.