Well, the show was awesome, and I decided to get my car dyno'd for $75 seeing there was no line early sunday morning. I am confused by the operators statement that my car is running rich by 4 lbs based on the Air/Fuel ratio. He said it should have numbers around 12.5 (I think) with vacumn disconnected. Car has 47 pounds of pressure now. Does he mean at idle? I have an AFPR, and know where the vacumn line to it is.
2600 rpm 95 HP 193 TQ 15.2 A/F
3000 rpm 164 HP 253 TQ 14.0
3300 rpm 195 HP 310 TQ 12.1
3400 rpm 203 HP 314 TQ 11.5
4000 rpm 227 HP 298 TQ 11.4
5000 rpm 248 HP 261 TQ 11.8
5500 rpm 250 HP 238 TQ 11.6
6000 rpm 244 HP 213 TQ 11.3
So I am disapointed the numbers are lower than expected. The operator stated that was at the rear wheels and at the flywheel with a 700R4 AutoTrans that I get a 23% loss. I start with high A/F ratio and then go into 11.5 for most of the remainder of time. Will making the fuel pressure leaner help in my HP/TQ numbers? I have read here that too lean and you are buyin new engine. Any thoughts would be appreciated.
Chris :seeya

 

WTH..... that sounds insanely high. I think 18% is usually the more agreed on value.

 

i think i saw that run on sunday you will gain hp and tq acros the board if i remember right you had the muffler eliminators if you were that one i thought they looked very restricted at the bends and the walker y is not the best either you would be better of with borla y and 2 and 1/2 inch flowmaster i had my 350 dynod a few years back and it made 290 rwhp so you should try to come close to that the cam then was a small hyd and i also had a set of stock afr heads

 

Scorp,
I had mine Dyno'ed at Carlisle also. The operator did say 17/18% on manual transmissions. You know more about this than I do, but, I wouldn't be surprised if a bit more was lost thru an auto. Plus, this guy lives on top of a dyno. Tough life, 75 bucks a pop to try and blow engines!

I was pleasantly surprised by the numbers on my 85 w/ 115K miles. not knowing the complete history of the car this was a learning experience:

229.1 HP@4500 and 323 TQ@3100 (Somebody dun sum work!)

That HP is despite an 11 to 1 air/fuel ratio from 3200RPM up.

Chris,
You do have to be careful about going to lean, that's why GM programs such a rich mixture at the top, to save the engine. I'm going to drop my fuel pressure a bit but since I don't have the ability to monitor the A/F ratio in testing, I will be sure to err on the rich side. Hmm... the A/F ratio seems to have a correlation to the condition of ones finances :rolleyes:

P.S. I'm moving to Columbia, MD in the next couple weeks. I'd like to hook up with a club or a group maybe head to Capital Raceway. I've never been to the track and would like to try before the end of the season. Feel free to email with any info please.

 

Chris,

I think I dyno'd right after you on sunday morning.

I dyno'd at 315 RWHP and 327 RWTQ air/fuel 10.5 @ 5600RPM
that guy said that I was also running a little rich, it should be around 12.5.

I'm going to run an autotap session, then go back to my stock MAF and see where I am. I may even try putting the Granitelli MAF ends onto my stock MAF and see what that looks like.

 

How were the dyno guys doing Air/Fuel Ratio testing? Were they sticking the wideband O2 sensor in the very end of the tail pipe? I didn't get close enough to see because I ran my car once on one of those flat bed drive away dyno's and the curves came out very jumpy and glitchy. Yet, the car tested fine before and after (by a couple weeks) at another dyno location that was built into the ground. They were telling me it was an ignition problem, I was telling them B.S. because it was the instability of the truck combined with the uneven ground and poor chassis support and suspension of the truck. I lost that battle. "We haven't had any problems with anyone else's car"... Until the rig got moved a little was what they meant... anyhow

12.5:1 is what you're shooting for. If they tested this way back at the tailpipe... I would discount the validity of the test. It takes a long while to heat these sensors to come to life in real operation. There is a huge temperature difference from installing a bung in the collector or running it at the tailpipe. If my gut reaction is right, the latter is the way they were doing it because I really can't see them drilling and welding the extra bung in place at the show. Nor would they remove a factory sensor for the test... so, my recommendation is to take the car to an established shop that has data acquisition capabilities on their dyno, weld in the bung and tune the fuel pressure just a hair while it's at the shop. 1 to 2 lbs adjustment is all you may need. Might I also add that feeling the "seat of the pants" difference as Lingenfelter does is quite difficult to discern. We're talking about + or - 10hp or so when it's tuned right. The plus is that the throttle will be more snappy, and you're gas mileage will increase a hair. Hope this helps! (p.s. Can I borrow some money ? I have the record at the local shop so far. I've got 27 runs logged into their machinge!) :yesnod:

 

Yes Scorp - I know you use those numbers of 18%, I was just as suprised to hear operator say the 5% diff between manual and 700r4 auto. I will be running at Capital Drag raceway (which is 5 mins from house) this friday if weather permits. I am going to attach the fuel pressure guage (Accel) and disconnect the vacumn line and lean her out some (maybe 2 or 3 pounds) after first run. See what the diff is. There is a group called the Gaithersburg Vette club that meets at SPort Chevy and an Annapolis one that meets at a chevy dealer near the bay bridge. I barely got out to, get to carlisle. Lots of daddy responsiblities. Any predictions on my E.T. times based on torque numbers. :bb

 

It was cool watching the dyno at Carlisle.

Here's the Corvette Annapolis web page URL: http://www.corvetteforum.net/clubs/corvannap/

There's also the NCC club which meets in Gaithersburg: http://www.corvetteclubofamerica.org/

They are running the Corvette Only drags Sept 15 at 75/80 Raceway in Monrovia MD. Tony's Corvette in Gaithersburg is sponsoring the drags (as he does every year). http://www.tonyscorvetteshop.com/

See you at the Drags! I'm hoping to take both the '70 and '87.

 

I'm used to seeing about 15-16% used for manuals, and 18-20% for autos.

 

First, dynos are all different and a different dyno in the same town at the same time of day with the same operator and the same car might give much different results. Rely on trap speed for a relative power comparison, although it has lots of factors too.

Second, how did they determine the AFR? I wouldn't worry about being 11.5:1. 12.5:1 is a generic ratio for power; some cars like more, some like less. The only way to really know is to datalog run after run with a WB O2 to figure out where your car is best. There is no way to accurately determine AFR (other than 14.7) with the stock O2.

 

I forgot to ask, what are you running for a chip? If you're using a stock or off-the-shelf program, there's A LOT of power left in your combo.

 

corvette1990 i predict 13:30 to 13:80 if you can hook it

 

I've always seen 20 give or take +- 2-3 for autos.

 

I am using a Fomato Custom chip, but Level Ten Transmission owner told me I am not getting a lockup signal from ground at D pin (or somethin like that). Chip PPL tell me the chip is using VSS for a signal (what ever that means). I plan on going soon to a local in the ground Dyno and get real O2 readings, from a bung (hehe). I guess they cant take my O2 sensor out cause that will mess up the computer. Hate to mess up the nice silver coating on the headers with weldly bits. My guess is that I have around 300 HP at crank, which is 55 less than advertised with a stinkin olde carb. Thought computerized injection and big intake plenumn and large tubes and large intake and headers and high flow CAT and muffler elims would more than make up difference. Oh well, its only money, and they print a lot of it here in the captial (DC). I will have to take y'all's advice and see real track conditions this friday at Capital Drag Raceway. Then I guess I will need drag radials to get traction under control. Its always something. Thoughts turnin to the numbers matchin stock block in garage. Do I want to follow JD 383 turn of events? :crazy:

 

Did they actually run the car, or burn a chip over the phone? Even with a Diacom sample, it's a shot in the dark without actually driving the car. I'll bet you have a lot more in the program. The car should have more. Take it to a test & tune and find out your trap speed to make sure the dyno wasn't way off.

 

I think you're not doing bad with that set-up considering a stock L98 auto will typically dyno somewhere around 200 rwhp... with your 250 rwhp, you have increased your flywheel HP somewhere around 60 hp... and based upon 250/.80 = 312 hp.... sounds about right. I think the majority of your increased HP has come from the extra rpm that your Superram/ZZ4 cam combination has given you, with credit given to your headers for 10-15 hp of that gain.

As a comparison, in one of my earlier stages of modifications I had 260 rwhp with 350 ci, 52 mm tb, ported plenum, accel large runners, accel base intake manifold, LPE 74211 cam, unported out of the box Dart 2 heads, hooker headers, with a 2500 rpm converter I was able to break into the high 12's with a trap speed of 105-106 mph with 60 fts of 1.75-1.80 at a 3500 lb raceweight.... you should be on top of those #'s with your pro-torque converter and sticky tires too.

Thoroughly port your heads and maybe move up that cam to the 74219 and I would imagine you could see 350 flywheel HP and probably considerably more if you do all of the little things that add up.

One other note.... it certainly looks to me like your dyno was with the torque converter locked up.... if it was unlocked, you should have had a big converter spike at somewhere around 3000 rpm, especially with your pro-torque converter...... whats the rated stall of your Pro-Torque ?

cheers,
Beach Bum

 

Couple of thoughts on your motor. I had a out of the box zz-4 in a third gen f-body - dyno'd at 275 HP , 339 ft lbs with a 700 cfm Holley projection tbi and Edelbrock headers. With the richness you're talking about I could see an additional 20 hp being picked up. First pull that day rich was 255. That car is gone now.

Next thought - I've got a GN with Felpro injection w/wideband 02. The dynojet 02 logs are accurate. The dyno o2 logs vs my o2 logs were the same. Your car is rich.

In tuning the f-body I leaned the motor out to the point that the car slowed down. Didn't hurt it. Didn't push it or keep it that way but the motor is still going strong. You can creep up on lean power. I was also always very conservative with timing advance. From the sound of the o2 log sounds like the chip isn't quite right. There's more power there.

 

Thanks for positive feedback on this topic. The Chip was done over the phone, not in person. I could take the auto train down to florida this winter to see Mickey Mouse with my son, and have chip tuned? The trans TC is a 2400 stall. I was lookin for a spike too on the curves, but all 3 were smooth up to 6000 rpm. Which brings me to another question. Why does the graph go from 2600 to 6K once when I know the car was shifting and really flyin on dyno. The operator seemed to walk slowly through the first few gears, then hammered it. What gear is the graph from (3rd???) in D. Not overdrive fourth I guess. I am toyin with the idea a nicer cam once these repairs are paid off, as well as better heads. But maybe, I will build up the original engine slowly in the garage. I am takin notes on what seems to be workin with you guys. So keep the idea juices flowin in the forum. :cool:

 

the dyno pull was done in 3 rd gear or whatever your direct 1 to 1 ratio is if he did the pull in 4th there is a chance of hurting the tranny there is only 2 disks holding overdrive 4th gear :yesnod:

 

i can't beleive no one has notice this guys name? 1990, as in 1990 speed density, the MAP sensors are really pickey about vac changes and the zz4 cam is quite a bit bigger than the stock emissions cam it came with, i really wouldn't be suprised to see this guy gain 30-40hp with a chip burned correctly. everyone seems to love ed at fastchips & i'd say it's not a bad way to go. he's less than TPIS & really knows what's up. mass air cars are much more adapt to change than the speed density ones, i'm sure we all agree here. i personally also own a 1990 car, only a 6spd and have looked into about everything possible within reason. usually you can get away with bolt ons really easy, {roller rockers, mini rams, or super in his case, open exhaust etc.} but the second the cam changes a chip does need to be burned. i'd expect to see you more around the 280hp range with cats or 295hp range without. get the fans on at 185-190 & a 160 therm & you should run like mad