well i just got my GTA on the dyno today. it was a dynojet and was done at speedtek here in ft worth tx. I feel like driving it in a lake right now. Please let me know what i could do to get more power other than the obvious of bigger cam. here are my #'s

Hp 218rwhp
tq 320

power curve was really flat from 4000 to 5000 and fell gradually from there with max power at only about 4000. i will try to scan my sheet tonight and post a pic of it. I am sure it may help to see it but i explained it as best as i could. I am not the dumbest guy out there but shouldnt i have some sort of power curve and not pretty much flat through them RPM's. well here is the rest.

Air/Fuel was really rich.

3500 rpm 14
3800 rpm 13
4000 rpm 12
4200 rpm 10

after 4200 it pretty much leveled of at about 10 and almost dropped to 9 at 5000. that is like way too rich right. dont know why so rich. I have no vacuum leaks. I just dont know what would make it run that rich. I mean i have better flowing heads and intake with mild porting on my plenum and runners. please help.

My fuel pressure was at 39psi.

here is what mods i have on the car and what i still have stock.

L98 350
SDPC Upgraded Vortec heads
SDPC intake
1.6 rollers
heddman shorty headers 1 5/8
deleted cats and air pump garbage. still have EGR
flowmaster exhaust
stock plenum and runners with mild port job done
stock air box
stock cam
do not have AFPR yet but getting one for sure now.

I know the airbox and cam is hurting me but i would have bet money i would have dyno'd more than 218: and that was the best run. other 2 were 216. Can anyone please tell me if this is normal #'s for those mods although they are not that much other than heads, headers, and intake, and small port job. I just know i am very disappointed:

 

I don't put much stock in dyno #s. They vary as the calibration is not identical everywhere. Even using the same brand of dyno, you can get different numbers from different shops. The only thing a dyno is good for, IMHO, is to show deltas for mods, not necessarily the raw numbers.

That said, get a tune. Your heads have thrown the tune off. You could be getting knock retard, but the dyno plot will show that via spikes.

What is an SDPC intake? TPI? Look for stock TPI dyno charts to compare the curve. HP will basically flatten out in the upper RPM ranges.

 

Friend with bone stock 210K 91 L98 put down 235 HP and 355 TQ. I would say something is wrong.

 

SDPC intake is just the aftermarket intake base made to bolt up with the vortecs. suppose to me much better than stock with airflow

 

tune being done in a few weeks. i knew it would help but didnt think a tune would hold me back that much.

also, i have done compression check before i went and all checks great. 150 to 160 on all cylinders

 

I ran my 350 TPI with stock injectors, Trick Flow Heads LT4 cam and Superram on the stock chip and it made alot more power stock. The stock chip is not holding u back that much. As in the other post with dyno numbers.. The individual found out that his fuel pump was bad and his distributor was messed up. That alone netted a ton of power I believe. Everybodys first reaction is the "Tune" but You should be at least at or around a stock number with a stock chip and aftermarket stuff.

 

You'll find that all out when you tune it.

 

Its a MAF car with better heads. How in the heck can he loose so much power with JUST heads.

 

thanks for the imputs.
now i want to have it tuned today but i have to wait. i dont have a clue how to do it myself so i am having mike do it from houston area

 

Do tell, what is the tuning procedure? Does it involve...oh, let's see...scanning? Sure enough.

 

 

I don't know who Mike is, and I'm not from Houston. I don't know what deal you have with Mike, but if he's a friend he should be able to help you diagnose the issues. First step in tuning is to scan. If he's worth his salt, he should be able to see what's wrong.

 

LOL, that all you have to say?

 

There is no possible way in hell just the heads are hurting him. So he tunes and picks up 30 HP. Thats what he should be WITHOUT a tune.

Add a mild compu cam from Crane with stock heads and intake ...Will that decrease power too on the stock chip?


There are PLENTY of guys running MAF cars with basically no tune. BuckeyeRoc comes to mind Running 12.1's with heads cam and intake with just the injector constant changed in the chip for bigger injectors.

 

mike is just a guy that has offered to do the tunning on my car. i am not from houston either but will drive a few hours to have him do it. many people in the south central region has spoken highly of him

i am sure he can tell me what it is and why after the scan but i was just wondering why in the hell my hp #'s sucked so bad with many of dollars spent to upgrade. i mean, i am lower than stock almost. 1987 l98 supposedly came with 215-225 hp and 310 lbs tq. i am at that now but with better heads and everything including full exhaust. i am just clueless and looking for some pointers to maybe why this would happen.

 

You just don't understand, do you?

There are different dynos. I've seen stock L98s dyno at 170hp. For all we know he could have gained 50hp. You just don't know. As I said, I don't put much stock on raw dyno #s.

The only way to know for sure if something is amiss is to get it scanned or to do a compare against an older dyno run at the same shop on the same equipment. Sure he can go do some small tests, like increasing the fuel pressure, but he won't know the real conditions unless it's scanned.

And, like I said, the first step in tuning is to scan. He could be getting knock retard, as I first stated, that would be the most obvious that something is wrong.

If it was running on less than 8 cylinders that would be another, but you'd hear that above all else.

Go to your tuner and have a look at it. All the tuners I know will do the scan before the tune. All the tuners that I know will let you know if something just doesn't look right in the datalogs. The only ones that don't are the mail order tuners, which he isn't going to.

 

I believe u have something else wrong in the ign. or fuel delivery.

U should see some kind of noticeable pickup by going to the vortec heads and intake alone.

Most stock 350 TPI cars I have seen run on a dyno have come from the 190's hp to about 220hp depending on the actual health of the engine. Ones that go above or below that are the occasional freak or ones that have other issues.

This is what I am saying from my experience on TPI cars and Dynojets(no other dynos allowed in this conversation) and also using realisitic correction numbers. U can make any dyno read high or low unrealistically by playing with correction factors. thats why it pays to use the same dyno if your comparing mods and the like.

Hitting only 218hp and 320 torque puts u in line with a good running stock 350 car.

Vortec heads are a drastic improvement from the stock heads as is the vortec base. I would almost have to believe you would see a real improvement there. I've never just done heads/intake without cam before so I cant comment on it personally.

I will say take the time and learn to tune your own Prom's, theres about a hlaf second floating around on a stock car if your get it tweaked out right.

Your AFR's were actually too lean at first and than almost to rich. Most stock cals I have run with my wideband, when entering PE tends to stay richer than 14, more like 12-1 area and than actually float to 11-high 10's as u go across the WOT tables.(they do this for cat protection) I suggest making sure everything on the car is 100% sound mechanically and electrically before going any further.

Then begin to work on tuning it for your actual setup and see what other gains you can get from it.

MAF isnt a magic cure for tuning. Will it work in some cases? yes. is it ideal? No! If u want to do it right your only choice is to tune it correctly Doesnt matter if your talking about a SD app or a MAF app. Knock is knock and improper AFR will kill u as fast as knock will.

235hp and 355ft lbs. on a stock 350 car? I'll eat my shorts if its on a dynojet with realistic correction factors and you can get it near those numbers for 3 runs.

Best I have seen personally on a dynojet was 225 and 315 from my car. (this is seeing about dozen 350TPI cars on dynojet) It has a catback and my tuning on it. Runs 14.40's at the track with horrid 2.3's 60 ft's.

Its just what I've done and seen.

later
Jeremy

 

That's at the crank. You have that at the rear wheels. Assuming you have a 15%-20% drive train losss, you're at 256hp to 272hp at the crank.

Do you know if that shop dynos low to begin with? That would be my guess, Mustang dynos have the "trend" of being on the low side. Of course, some shops dyno high.

 

I agree and understand where your coming from, but if a stock L98 is putting out 170, something is out of whack with it. Stock, they should be putting about 215-225 at the wheels.

MAYBE somehow its out of tune, but I very very believe that a set of heads would DECREASE power in the first place. Yes theres minor tuning you can do with the timing, valve last, FPR, but I hardly believe he would need a "custom" tune for a basiically bone stock motor.

 

I've seen cars pick up 30 - 40 HP at the wheels going from 10.0 A/F ratio now leaned out to 12.0. That fuel is what's killing that power. A perfect scenario is 14.7 at idle to 13.0 at WOT. With your car running THAT rich, I'm surprised you didn't foul your plugs.

What kind and size are your injectors?

Did it set any engine codes?

What kind of shape are your plugs and o2 sensor in?

and finally, you would REALLY benefit from an adjustable fuel pressure regulator. I recommend the Holley billet reg., it's adjuster is a billet dial that you can spin with your thumb and it beats fishing a little wrench in there to adjust it. I run the Holley on my motor.

I use Datamaster to scan / datalog by the way.

Also, for your Vortec heads, I recommend you use NGK TR-55 plugs. You can get them at o'reileys auto parts: get that exact part/model number in v-power NON-platinum.

If you are running the stock injectors, that could be your problem. Those are crap and tend to stick open at times especially with age. That's how I blew the stock motor in my car. #7 injector was stuck open, gas washed the rings, gas then thinned oil, and then I spun several bearings, motor was knockin' like hell............... time for the new one.....

I use #24 SVO's in my new motor.

Mechanical problems need to be corrected first. Tuning will not cover up or cure mechanical problems.

 

170hp on a Mustang dyno stock is not unheard of. :shrug: Dynojets are what most people on this board throw around. Mustangs dyno lower in general, I haven't used it myself, but friends have.

I don't believe there is anything other than a custom tune. Mail order tunes work to a degree, but assumptions are made.

Believe it or not, I think the dip down into the 10 AFR is "stock". It was on my car. It annoyed the crap out of me. His listed AFR basically matched my stock AFR. I dyno'd a good bit higher, but was on a Dynojet, and I believe my dyno ran high.

Pulling plugs is a sure fire way to diagnose, but I've never been good at it. And from what I understand you have to do the run and immediately shut down.

I think the best thing to say is get it scanned. No arguments, scan it. There could be a ton of things awry, and it could just be that the dyno isn't calibrated properly. If you can't do it yourself, your tuner friend can.

Definitely, the stock injectors suck. You can take a multimeter to it to measure the resistance. When the stockers go, the resistance drops.

 

Also, did you delete the cold start injector?

If you haven't allready, this is another possible source for all that extra fuel you are experiencing.

They can stick open too.

If you can afford to do so, get a set of after market TPI runners for a 90-92 TPI. Then remove cold start injector and cap rail with the correct plug. If you do a search, you see exactly what cap to buy and where to get it. Now that fuel rail is sealed, swap runners and you're done.

 

I take that back. I looked back at his sig and it was 225 /335 with a best of 13.6@102.7 These runs were all consistant on a dynojet. www.bigshotdyno.com. All 1/4 runs were at Dragway 42 in Ohio. Hes Jayzee over on the other thirdgen boards. Its fast for 210K miles.

 

1bad91z:

the motor is very sound mechanically. atleast it was when i had it looked at by a shop before i added the heads and intake. i brought short block and had it looked at. all was well.

i am using ngk plugs and also have new wires, cap, rotor.

i do still have stock injectors but tested good also but that could have changed over the last 200 miles. the build has only 2000 miles on it.

before the rebuild and after the rebuild, i can tell the car did pick up some but was only minimal from what i could tell. it didnt really impress me. that is when i started testing and looking at sensors, vacuum, etc and changed all hoses and sensors tested good so kept them on.

i havent deleted the cold start but plan on it before i head down for the scan and tune. i will also have fpr.

i have tried to put a pic of the dyno sheet on here but says item too big. i will play with it till i get it

 

dyno

 

A lot of people say dynos vary. I have had my car on three different dynos and got very similiar numbers. One time I got 245rwh/326rwt, 242rwh,317rwt,237rwh,323rwt. Even though I disprove the theory somewhat I would have your car dynoed somewhere else.

 

well i agree with 1bad91z

you gotta get that air fuel ratio figured out. there is alot of power to be picked up there.
and stock fuel pressure is like 42psi i believe. get the afpr and try tuning it with that. also look into your injectors... get them cleaned up/checked out or buy new ones. make sure your MAF is good to.

whats your timing set at?

next thing to look into is runners to go with those higher flowing base/heads. that can help out too to help lean out the rich ness at higher rpms. you have lots of fuel but no air. stock runners are restrictors and killing that motor.

 

a good tune is going to wake your motor up
that 10 to 1 is too rich. i can see mike working a bin right now that on the first try will be way better than whats in there now.
you really want the better injectors & good runners along with the other stuff before the tune, if you do them after it will throw the tune off.

 

my maf is new and is good. i have checked all sensors today after work. everything is ok.

i am going to buy afpr this week. i tested my pressure after thr run and it was 39psi. i am also going to check the injectors again. prob just buy new 24lbs.

my timing is set at 6deg btdc

i will look for runners. thought about going with tpis bigmouth plenum and runners. if i do, do i have to do any work to the base such as port matching. this mess can get very expensive.

thanks for the reply and suggestions.

 

then i may have to wait on the tune a few more weeks longer than i thought. i was new to the tpi set up when i started and didnt know what to get first and so on so i dumped a ton on heads,base and headers first.

mike, i will get with you on when would be best for me to come now. new runners and such is going to put a dent in my pocket book for now. prob tune in feb ok.

thanks for imputs.

 

That graph is completely wrong. I thought it had some semblance of a normal run, it has nothing like it at all.

Also, where are you seeing the 10:1 AFR? I don't see it on your plots. Your AFR seems to be 11.75-13.

Out of curiosity, were your heads assembled properly?

I hate to say it, but scan it. You really can't tell what's wrong from that plot and the info you gave. It's totally messed up. How did you check that your sensors are working?

 

Yea. That graph looks horrible. Its not even a graph.

I think once you nailed it the car started out at 218 HP. Not maxed. It should go up.

 

A well tuned stock '97 350 should pull about 195 RWHp (stock rated flywheel Hp is 225), you pulled 218 with your listed mods. I agree it should be a bit more, maybe about 235 to 240.

I think (as others above) that tuning will help, but dont expect too much.

Buy a engine scanner, it is very helpful in determining what could be your main issue. I would set the timing at 10* BTDC and set the fuel presssure to achieve 12.8 to 13.0:1 at WOT. You could also remove the screens from the MAF sensor. You can increase the flow of the MAF by about 15% by removing the screens. BUT, be very careful here, dont ever drop the MAF or let anything full down into it.

I located my old dyno run sheets:
The best my '87 car would pull with the 350 stock bottom end, ported factory plenum, high flow runners, AFR heads, FMS 24#/hr injectors, AFPR @ 46psi, cam, etc, etc, was 242 RWHp.

 

91z28

sorry about the 10-1 on the first post. i didnt have the graph next to me when i posted. just went off memory.

the heads were assembled by SDPC so i assume they were assembled correctly. they came assembled when ordered.

i checked all sensors with volt meter. all were withing standards. the maf and tps and iac are new also.

that was my first dyno so i dont really know what the graphs are suppose to look like. just a fairly newbie.

I know saying at first 10-1 is alot different from what 11.5-1 is a bit drastic and i apologize for that as i didnt have the graph next to me. i was so upset with the results i got ahead of myself.

just ignore me and look at the graph

 

where can i buy a scanner and about how much does one cost.
that way i can scan it and post reading on here for more help of what is going on so i can fix some issues before having it tunned

 

The Vortec heads don't like lots of timing; try bringing your initial timing down some. I'd start at 0 and work my way up to probably no more than 4 degrees advance. Probably shouldnt have more than 32* total, but you'll have to deal with this is chip tuning.

 

it will be best to have the runners port matched to the plenum and base. its easy to do. you can do it with a dremel tool and lots of sanding drums. it takes abit of time, depending on how big you have to go or want to go, but its really easy to do.

 

the sdpc base is suppose to have bigger runners in the base, they say the larger aftermarket runners bolt right up. i know i can and will port match my plenum to match runners and also siamese the plenum also. i am going to post a thread looking for runners and see what i can get my hands on. i just didnt know the factory runners were that restictive. i am going to get some runners and afpr and port match plenum and then get the tune done and see where i am at then. i may get a another dyno after installing runners and such and see the results just with that and then again after tune.

this will give everyone a chance to see what both did. well thanks for the reply.

i guess i can also check valve lash to see if i over tightened or so but i am 99.9% sure i didnt over tighten

 

I would probebly start at 6* Stock timing and go from there. Checking valves can never hurt. I'd go 1/4-1/2 turn on the rockers once the ticking stops. I was able to start my gf's car and it sounded good but had little power. I found out I have way over tightenem them and backed off 2 full turns and they readjusted them.

 

6* would be fine to start on a stock type of head, but the Vortec heads like less timing. 6* initial is usually them max that guys run with Vortec heads.

 

http://www.moates.net . Get a cable or the entire chip burning package and run a program, hook it up to your laptop and log away. Good thing is you can tweak it a bit while you're doing that.

It's funny that your curves are identical on every single run. Your curve looks like somebody elses that posted a while back. Just flat all the way through, you only got a variance because of the pedal mash. It's funny that it then backed off.

If you can find the person that posted a similar plot, you may be able to find your resolution.

Definitely check the lash. I don't use the running method, I use the static method, and have never had a problem. A little bit on the loose side will give more power than a little bit on the tight side. For lash to effect it that much, it would have to be overtightened, which will cause other problems if you keep running it.

This is going to be very difficult to do without a scan tool or dyno tuning (repetitive dyno runs, but that's expensive). You can set your distributor to 0* timing if you think you are running too much timing. That could very well be the case. What the distributor setting does is it retards the entire curve by 6*, as 6* is the stock setting (what you currently have it set to). If it "feels" better you may be on the right track. With a scan tool, you'd see knock retard immediately.

Check the basics, fuel in all cylinders, and spark on all cylinders. Start with spark and fuel after you check the lash. Vacuum leaks? Does your engine stumble?

Easy way to check fuel. Hook up a fuel pressure gauge. Turn the key to on, but don't start the car, let the fuel rail prime. Use something to each injector, and the fuel pressure will drop. There's a tool you can buy to do that (http://store.autotoolexpress.com/fuinpute.html it's not cheap). You can probably rig something up by yourself, but don't hold the pulse too long. Spark, pull the spark plug boot off the plug, and spark it against something, just not yourself. BTW, you may flood the engine doing the fuel test that way, so let it sit a while after you're done with that. The other is to pull the rail, prime it and shoot it into a bucket....or send it off to someone like Rich@CruzinPerformance.

Don't worry about the induction now, you've got other problems without adding more stuff to it.

 

91z28350

i will adjust timimg this weekend and set it at 0 and see if it helps and go from there. the car does stumble a little when the motor is cold but is fine when motor is at normal temp. it is not a bad stumble thought. just feels like a little miss or something.

i will also check and readjust valve lash just to make sure.

i will test injectors. i have access to pulse tester. i have checked spark already and all is good.

thanks for the info.

MAN I LOVE THIS SITE

 

what cable do i need and is a cable and a laptop all i need to scan it and see what is going on.
sorry if it is a dumb question but i am like fred flinstone when it comes to the computer aspects of my car. i have never touched anything other than the paperclip test to check codes.

 

Dude....

Leave the timing at 6*.

11.5 or so is ALOT better than 10 to 1 A/F ratio !!!

Just delete the cold start injector, and install your AFPR. Set FP to 39 PSI at idle with vac line disconnected.

DON'T siamese the plenum. Call an engineer at SLP. He will tell you the same thing. If you want to port your plenum, just enlarge port diameter to match your runners and throttle body only if you have larger runners and throttle body. But DO retain individual holes on the sides of the plenum. SLP has done EXTENSIVE flow bench testing on this issue, I believe they know what they are talking about.

Also, you said you are using NGK's, but are you using TR-55's ? A NGK UR-4 (is what is correct for a TPI 350 with L98 Heads) will work in a vortec head, but it is not long enough to reach the combustion chamber fully. So part number in this case is very important. What part / model number of NGK plug do you use?

Also, every motor is different............ period. My motor likes 7* base with 35* timing max in the PROM and I don't get any knock retard. Yes, my vortecs have alot of work done to them, but the combustion chambers weren't modified. I've also seen some vortec TPI cars not like anything over 6* base and 30* max in PROM. Hence, your car has to be custom tuned.

Just let me know when you are ready to bring it down or if you have any more questions. I will scan the car as soon as you bring it down.

Mike (1bad91Z)

 

i am running ngk ur-5 is this bad? i am going to buy the tr-55 this weekend if so.

 

ok, just researched plugs. here is what i found.
ngk ur4 14mm .460" reach

ngk ur5 14mm .460" reach

ngk tr55 14mm .708" reach

the ur4 and ur5 have the same reach. i guess i am running wrong plug. the 5 is for stock heads. i will change this weekend.

one problem solved and many more to go.

 

Def need the longer reach. I bet thats your main problem.

 

See, told ya about the plugs!

Your car will run ALOT better with the correct plugs (TR-55)

A UR-5 is a "colder" plug than is what is required for a L98 head. A UR-4 is a hotter plug with the correct thread and reach for a L-98 head.

Vortec's need more reach, hence TR-55.

Let me know how she runs when you change plugs.

 

well i changed the plugs today. put in ngk tr-55. it runs better and i can tell there is more a little more power and torque. it also smoothed the idle somewhat also when motor is cold.

i am looking at some large tube runners and will prob buy them in the next few days along with the afpr. she should wake up more with those also.

mike, it will prob be sometime in feb now till i can go down there for the tune. after the runners and fpr, i will have to stash more cash. i will let you know a for sure dates shortly after i buy the runners and such. want to have everything done before i get it tuned.

i cant believe i was running wrong plug. learn something new everyday.

again, thanks for the imputs. i will post new dyno before tune and after tune. that way everyone can see the benefits of a good tune.

 

eeekkkk I got 251/318 rw hp and TQ with the stuff stock untouched heads and a ZZ4 cam with NO tuneing . It still though it was a 305 with 19 lb injectors. But I guess dyno's vary. What cam were you runnnig in that setup ?