All my knowledge of building a faster car is carburator Mustangs. I am new to modifying my tpi corvette. I bought it stock except for flow master chamber 2 exaust, K&N air filter. I just bought a innovative Chevrolet Corvette performance chip, Hedman Street Headers 68440, Spark Plug E3's, and new spark plug wires; the ladder two for a tune up. This will be my first time installing a performace chip so I am hoping its a good start. With the fox body mustangs there were so many different modifications to buy and it seems like i am limited with the corvette and especially with the prices so I want to choose wise.

I am wanting my automatic to be quick maybe lower 14 seconds at least. I am looking for advice, on the chip, other modications I can or should do? Any information would be awesome. And I am curious, will I be able to use my laptop and program to change around the fuel, air etc with the chip?

Thank You
Eric

This is my 91, that is my dads 73 were building, my brother has 75.

 

Well the chip is worthless except to change fan settings, all it did was bump timing curves. If it didn't change the fan settings then it was truly worthless and should come out now, because they may have bumped the timing so much that it will knock once it reaches normal operating temperature. If you have the software and knowledge to reburn and tune yourself then that is an option.

Upper 13s can be achieved right now, just work on your 60'. Doesn't require radials, can just be a good street tire. Stock TC doesnt help, and would be better to stall around 2000-2200 but it can be done. Wait to change the TC until you have more of a plan.

Next question is what power goal and/or what end result do you want from the car?

 

Are you talking about the same innovated chip I purchased? I figured it would come in handy for when I change to a bigger throttle body, honestly I am not sure if the HP, fuel mileage gains it promotes is plug in play automatic or thats if I can figure out how to program it to perform better than stock by telling it to increase the fuel and/or air. Like i said I am totally new to the fuel injected motors. Its going to be a big learning curve. I am told that once you figure out how, they have the same if not more potential than carbs.

Stock it says 240 HP, I would like to match the ZR model which is probably 345HP. I probably wont touch the transmission as I wont be taking this one to my road race track I live by but maybe for fun, I will definitely take this to the drag strip to see what I can pull off on the 1/4 mile. Its going to be a fast cruiser that I can take to the roads when with my dads 73 and my brothers 75. They are both close to finishing their NEW motors and they are pretty high profermance with after market heads and a little better cams. Im going to have to make up the horse power from not having those 2 upgrades by little things like my full exhaust, chip, what other tips I can get off this thread or online.
Thank You

 

how well did the hedman street header 68440 fit?

 

Welcome to the Forum.

I'm surprised that you struggle to get into low 14s?? What is your usual DA/elevation?

Some things I did to my '88 to get mid-low 13s at Englishtown (~at sea level):
-since you already have the K&N, now open the air filter lid
-install a 160deg T-stat & fan switch
-do the TB coolant bypass
-install an AFPR so you can bump the fuel pressure for better A/F ratio at WOT
-remove the "frisbee" from front of your engine, if your '91 has one
-arrive at the strip with 1/3-1/2 tank of fuel
-remove the spare & jack (AAA will rescue if needed)
-pick up a book on TPI/fuel-injection

Indeed a 2k RPM TC will bring down ETs by lowering 60' times. I was able to pull 1.8s in 60'.

These mods along with you hi-flow exhaust (if FL headers) should put you around the 300chp mark, good for well into the 13s.

Good luck and have fun with your '91.

 

Sorry Eric. It ISN'T a good start. If you can, return the chip. That and the E3 will net you less gain than if you lost 100 pounds of weight. If you want to, spend some money on a good intake. That would help better. After that, assuming the cheap headers are up to the job, a tune ON A DYNO or at the very least, some sort of datalog. The tune in a can or off the shelf crap is a waste of money. It promises you "UP TO" X HP increase. That means nothing to 30, most likely nothing unless it comes at some heavy price.

 

I just purchased the headers last night. It got pretty good reviews except, you have to sand the shipping paint off and then repaint them. I know its going to be hell to install though, its tight on my 91

 

Yes

You don't need a larger TB. I did, but I have a 398 with a Superram on it.

Yes they do, over a wider RPM band theres more things you can do.

So the Innovated chip goes away, you only need to be able to reprogram your stock chip. I'd keep the stock as a backup and try to reburn the Innovated as you tune it, if you are the one that is going to do it. But you have no mods done that require a chip change.

For about 100hp, I'd redo the entire exhaust as you've started. L98s cannot exhale at all from the factory. Headers, a new main cat or duals. Random Tech is a good cat maker. Get the factory catback off, and pick another based on sound preference.

I'd have the stock D-port heads taken off, ported, and new valvetrain components put in. Your heads are pretty good, 350hp is about their limit in factory shape, but at this age the valvetrain should be redone and a new cam choice installed for this power level. Porting will flow more for the cam. 1.6RR is another need that gives some power.

Cam depends on intake choice. TPI is not conducive to big numbers, the runners are too long and the engine cannot inhale. At a minimum you will need a new intake base manifold, plenum porting, siamesed or larger runners like AS&M. Much stuff is no longer made, so keep an eye on ebay. If I were going this route I'd probably go with something in the 210/220@050 range like the TPiS ZZ9 or Accel 211.

A different strategy is go with another aftermarket base like TPiS Miniram or Accel Superram, modified Holley Stealthram, etc. Each has its own cam choice to optimize the combo. After the cam is changed, a custom chip burn is required.

But you won't be happy with the off-the-line feel until you swap out the TC for something in the 2000-2400 range. A miniram intake will also warrant this change as well as a possible rear gear change.

 

]Welcome to the Forum.
I'm surprised that you struggle to get into low 14s?? What is your usual DA/elevation? I haven't taken it to the track yet, low 14's is my goal. I am in Tulsa Oklahoma so yes from what Ive read in articles times are slower here. My experience is a 85 mustang covertable 5 speed 302 gears were 3.08, stock w/exhaust it ran 15.50. Then I took a motor from a 1991 mustang because it had the better pistons I think they were forged, I installed edlebrock RPM air gap intake, holley 650 double pump carb, look tube hooker headers, my stock 91 heads were ported a little bit, I put the F303 cam. I ran a 14.40 with those modifications using the same 3.08 gears.
Now this corvette stock feels like a 15.10 to 14.90 by going off how my mustang felt. I haven't ran this car at the track.

Some things I did to my '88 to get mid-low 13s at Englishtown (~at sea level):
-since you already have the K&N, now open the air filter lid
-install a 160deg T-stat & fan switch
Fan switch? Are you talking about putting a switch inside so I would turn it on and off when I want? or an automatic switch, if so where would it go?

-do the TB coolant bypass
Is there a guide online on how to do this?

-install an AFPR so you can bump the fuel pressure for better A/F ratio at WOT
As you can tell I am new to EFI because I don't know what the PR stands for?

-remove the "frisbee" from front of your engine, if your '91 has one
-arrive at the strip with 1/3-1/2 tank of fuel
-remove the spare & jack (AAA will rescue if needed)
-pick up a book on TPI/fuel-injection
I completely agree, I will do this for sure.
Indeed a 2k RPM TC will bring down ETs by lowering 60' times. I was able to pull 1.8s in 60'.
These mods along with you hi-flow exhaust (if FL headers) should put you around the 300chp mark, good for well into the 13s....

Thank You!!
Good luck and have fun with your '91

 

aklim, How come it isn't a good start? I am asking because I am confused, I am always told hey you gotta get that exhaust, performance chip, filter. I always do my exhaust first because of the sound. The filter to me isn't going to do a much if anything but they are a lot better and lifetime warranty. Now the chip is what I don't understand BUT I am hoping I can connect to my laptop and get air/fuel information and I am really hoping that I can change it to make a what I got perform better by calibrating my air and fuel. I agree on the intake, I know what I am doing on my intakes, heads, and cams. ITs the EFI part I don't know yet. The headers are basic but they are going to be better that the crap stock manifolds that come with these cars-they got good performance reviews and sound from 90% of the reviews so Im feeling good about that purchase, I wanted the better plugs and wires because this car needs them, they are in bad shape.

 

Thank you Vader, this is exactly what I was hoping to get from this thread and forum, I really have a good idea or at least a better idea on how to tackle this EFI Corvette. Much apprecaited for your time.

So the Innovated chip goes away, you only need to be able to reprogram your stock chip. I'd keep the stock as a backup and try to reburn the Innovated as you tune it, if you are the one that is going to do it. But you have no mods done that require a chip change.
So at the moment this chip wont calibrate my air/fuel for better? I understand what your saying that when I go to add big mods like heads, cam intake etc that this will come into play? Its crazy that a lot of people and lots of advertising and articles talks about how you can gain some HP and some gas mileage right off your stock vehicle with, my ultimate hope was yeah a few HP, maybe better gas efficiency but I wanted to be able to see on my laptop what my air to fuel is doing.

For about 100hp, I'd redo the entire exhaust as you've started. L98s cannot exhale at all from the factory. Headers, a new main cat or duals. Random Tech is a good cat maker. Get the factory catback off, and pick another based on sound preference.
Well in my state, Oklahoma, we don’t have any rules and we don’t have catalyst so right now my manifolds Y and then Y back out to dual flowmasters. I was hoping I could just get rid of the Y’s and do and H pipe there. I had one built on my mustang and I loved the sound it made. Would there by any issues on doing that to this corvette? I always wondered why the Y’s

I'd have the stock D-port heads taken off, ported, and new valvetrain components put in. Your heads are pretty good, 350hp is about their limit in factory shape, but at this age the valvetrain should be redone and a new cam choice installed for this power level. Porting will flow more for the cam. 1.6RR is another need that gives some power.
If I had my stock heads ported, would I need to upgrade anything at the same time? Mass air flow, throttle body, anything like that? I would be happy with 350 HP, is that Max for the stock heads or Max for the stock heads ported?

Cam depends on intake choice. TPI is not conducive to big numbers, the runners are too long and the engine cannot inhale. At a minimum you will need a new intake base manifold, plenum porting, siamesed or larger runners like AS&M. Much stuff is no longer made, so keep an eye on ebay. If I were going this route I'd probably go with something in the 210/220@050 range like the TPiS ZZ9 or Accel 211.
Okay I will take a look at those, thank you.

A different strategy is go with another aftermarket base like TPiS Miniram or Accel Superram, modified Holley Stealthram, etc. Each has its own cam choice to optimize the combo. After the cam is changed, a custom chip burn is required.
Okay, I need to figure out a good cam for my goal of a street car with the occassional drag track and road racing at Hallet speedway on weekends. I really liked the Ford Racing F303 cam I used in my mustang so I can match up the specs from that to one of these brands. Thanks

But you won't be happy with the off-the-line feel until you swap out the TC for something in the 2000-2400 range. A miniram intake will also warrant this change as well as a possible rear gear change.
I am glad you mentioned that, I believe I have 2.70 gear, which is what came with the automatic trans vettes that year, the manual trans came with a 3.08 I believe. I really would want a 3.50 range, which should still be good for the daily street.

 

No at the moment the Innovate chip isn't really improving anything at all for you. At most its changing the timing curve, but its not drawing any more air in or out of the motor, that is the L98's problem. It cannot breathe. I can bump timing around and make some power at 2000 rpm at the expense of it at 3500 rpm by messing with timing, or I can just keep advancing the curve to the point where it'll knock in regular driving once it even hits 200F. Thats why some tell you to change the t-stat to 160 with their chips. Either way, youre not really gaining squat. Adding mods that the tune isn't compensating for with more air or fuel doesn't help either, thats why it has to be custom or not at all.

H-pipes arent used because of packaging reasons basically. You can do an X pipe, same concept really, or try to bridge a true dual setup if you want though.

350 crank HP is about the limit of stock heads ability to flow. Porting can get that to about 400chp. If i were taking them off for valvetrain to be redone, I'd have it done and never mess with them again. You never need to upgrade your MAF or anything else on a 350 SBC. Stock 48mm TB is fine too.

You would have 2.73 in a D36, which is not terrible if you have that, for an L98. 3.07 is about optimal for the L98/TPI style that makes so much low end grunt, in an A4. The manual ZF6 would have 3.45 in a stronger D44. A miniram intake would make its power on the high end rpms, so the gearing should be lower like 3.45/3.54/3.73 in an Automatic. Adding 3.54/3.73 to the TPI style would just get you out of your band quicker and wouldn't really be optimal unless you just run 1/8mi or 0-60 passes. The TPI-style intake kills the power by about 5000 rpm remember. This is getting into cam and intake choices, which is why I said the intake choice was most important. Changing the TC instead gives the same feel but less of such penalty.

 

Your first 50 hp can be had with exhaust, fuel pressure and airbox mods. After that, you need a strategy. Revs, cubes or both. Cost obviously increases from left to right.

Revs starts with intake mods. Siamese runners, base plate, lt1, superram or miniram. Next is cam. Final is heads. I went this route and I'm in the high 300's with SR, ported 113's, xfi268 cam, lt's and true duals the whole way back with crossover. You need a chip at that point but it needs custom programmed.

Cubes is either a 38x stroker or 4xx sbc in most circumstances. I've got a forged internals 406 on the stand for phase 3.

Remember bigger is not always better. Make sure you know your goals before you start so you don't end up with a 350 with a stock cam and 227cc race heads.

 

Your first 50 hp can be had with exhaust, fuel pressure and airbox mods......
can't all of that be acheived with simply putting on a rpm air gap intake. 650 double pumper and good headers with cat delete?
according to super chevy magazine anyway, they did exactly that. but used a 750 dp instead of 650... dyno test was 365 hp and almost 400 torque and with the tuned port is was around 320 ish hp or so.. if i remember right, pure stock l98 engine with edelbrock rpm air gap intake carb and headers. nothing else done at all. that is a significant improvement, maybe lose some mpg but if you drive a corvette mpg probably isn't really a concern.
so your stock l98 with original tuned port is pretty close to 325 hp at the flywheel. you can spend thousands on all the fancy high tech crap or just buy what it sounds like you already know well for like 1500 bucks and be done with it.. you are the only one who can make that decision. and who really cares what anyone else thinks of your car but you

 

At your level, I am not sure the exhaust is really a limiting factor. As to chipping, you are probably ok with just the cat back system. If you are doing headers, intake and cam, you need something with a goal so the tuner can help you achieve it. You cannot mix one set of heads with a cam from another system and expect optimum performance when you have a sucky intake. I would first do the intake and headers before I even consider a dyno tune. Dyno time is expensive so you might not want to just blow it on say 5 HP gain with your headers. As to the sound, I have no idea what to say. I would want something as quiet as possible and others would want it to be sounding like some older muscle car used to because they didn't have the technology to make power without noise. As to the plugs, just stock Delco or NGK would be fine. Don't need to buy E3 since it probably costs more money. At this level, E3 plugs are more expensive and fanciful sounding but won't net you any real power. So it is money for absolutely nothing.

As to the chipping, it has to work with the system. You can't throw a cam that won a race yesterday with a set of heads that someone said was excellent and an intake that was great and hope to have the chip maker do something. You need to find a chip maker first. Solicit his opinion on what SYSTEM he has built and what the known results are. After it all comes together, dyno tune it. Getting a chip that someone says might make "UP TO" 50HP isn't good since it isn't matched to what you have. It needs to be optimized for YOUR system and not mine. I could give you my chip and if it starts and runs decently, it will be a miracle. It runs great on my car though but that is a different system.

This Innovative Chip, is it from "gainmpg.com"? If so, ask yourself how it works. So I sell you a suit for someone your height and weight. Think it will fit as good, if at all, compared to someone measuring it? Bottom line, if it is cheap and easy, as for a guarantee and a way to test the claim.

 

How would it calibrate without knowing what you have?

I think Random Tech, which I had is out of business. It was obvious when I had a Borla Catback with no or hollowed out cats. Drone was unbearable so I put a cat on. Besides, at your level, you aren't really going to make enough power that it justifies taking the cats off. As to trying to get fancy with a H-pipe, sure you can but you may lose some ground clearance. You don't have that much to begin with. I have TPIS headers with a cat and a Borla 3 inch for the 304 SS and less restrictions but if I have to lose any more clearance, driving is going to be a PITA with any bumps. It already is difficult with the bumps and potholes.

I don't think you are going to exceed the MAF at this time so why bother spend money? IF you are going with a TB, check with the tuner if it even helps. Of course, if it comes with the intake, sure. I bought my Accel Superram as a kit from LPE but I was going a little further than a 350.

Find your tuner first and see what he thinks will play nicely together.

Superram will fit but Holley Stealth Ram will need a hood scoop.

For mostly street, I really wouldn't go more than a 3.73 or you will just burn gas for very little.

 

As you can see there is no shortage of opinions on increasing power. Use the search function and search '300 hp L98', there are many threads on making power including one I wrote about my '91 making 310 to the tires (~365 crank) with stock heads, tb, injectors and a crappy, cheap as hell exhaust system. Having an automatic car I would do a stall and gears first, you will see a lot of improvement there.

 

Well the good news for you is a 91 automatic Coupe can hit LOW LOW 14’s at close to 100mph BONE stock if it has the 3.07(G92) axle and performance mufflers it had 250 horsepower 245 with the standard 2.59 axle 90-91’s Vette’s were the fastest TPI engined cars...mid 13’s is easy with some free mods, a couple bolt ons a looser torque converter and some drag radials

 

91’s are speed density and didn’t have a MAF

 

Doh! I got caught up in his question. Still, from what I see, Innovate makes the "chip" which is some sort of thing you splice into the MAF to change the readings. Guess he will have a hard time doing that. Must be why they don't post instructions on the site if it is THIS. Oh well, I was going to use it myself. Nothing I like better than cheap and easy performance and eating flying pigs.