Damon

Max Race- I can totall understand that story. I LIVE AND BREATHE street engines. The number of times I have found simple stuff holding an enigne back AS INSTALLED IN THE CAR is a lot. Fuel supply and voltage/ignition problems are almost always the culprit. At high speeds I can understand hood scoop/air inlet problems also causing hair-pulling situations, although my motors don't often get connected up with true forward-facing scoops.

The difference between and engine dyno and how it runs in the car under actual racing conditions can be HUGE depending on stuff just like that. That's absolutely the truth.

My 78 Malibu street cruiser with the blower motor puts out 390 to the wheels. Put on the air cleaner and I bet I whack 10-20 HP off that number. Why? Becuase of hood clearance I have to run a too-short air cleaner assembly that I just KNOW and can FEEL is restrictive. I have to do this just to fit it all under the hood. In my case it's a trade-off that I knew about going in and I accept it. In a race car stuff like that can drive you bonkers.

Anybody not running an EASILY VISIBLE fuel pressure gague and voltage gague on a race car is just ASKING for frustration. I do testing on my street cars with them hooked up temporarily (often duck taped to the windshield) to make sure all is well, then I take them off when I'm satisfied that everything is working correctly and running to the best of it's ability.

CANTONRACER

I help out at my local Dynojet dyno shop a couple of times a week.

It amazes me how people who swear up and down that the new part they just put on makes the car so much stronger...then you dyno it and see like 1 rwhp difference....

I enjoy seeing cars dyno because that is where the bs stops..just like at the track...

But from what I have found...some cars that are boosted are actually putting down lower #'s...like my Lightning, dynoed last night...put down 358/430 SAE..only 4 more rwhp than last time...but my truck is stronger on the h-way...under a load I make another lb. of boost and my modified airbox works when my truck is moving...something a dyno does not do.

And I have had lately some problems coming up with an equation with my truck. I G-teched it last night...0-60 in 5.12, 13.56@108.4...you plug my rwhp vs weight of 4900 lbs..and crap aerodynamics...I know G-techs are high...but let's say it runs 104 in the 1/4...the numbers are not working out.

But as a tuning tool...a dyno is hard to beat unless you have the ability to simulate the conditions every time. Same engine temp, air temp, start rpm, everything the same...try that at a track when there is a 20 deg drop between a few runs.

andy katzelis

I can't remember how SAE hp is derrived; but It seems like it's lower. In general wasn't it an attempt by the big three to avoid insurance problems with customer's cars?

I assume your using the pro-stock et formula. Don't give up on them; they are based on a nearly perfectly tuned (all components match) naturally aspirated prostock car, not a supercharged truck.

Based on MPH if you can acheive the et they did, you're doing an excellent job with your combination (matching up the entire drivetrain). Another excellent class to compare to is nostalga super stock, those men know how to lay it down.

I just got the G-tech for christmas, finally convinced the wife street tuning is safe, so I haven't correlated the numbers to the dragstrip results. I will. Excellent tuning tool, just like a dyno. But the strip is still what seperates the men from the boys.

CANTONRACER

SAE on dyno's are to give a more fairer comparision against other dyno's numbers. STD is what the vehicle made in the current conditions...like my truck really made 365/440 STD...but I guess I am a guy that likes to know how it does against others...sorta like putting the weather, elevation, DA(if known), the day I race my car...keeps it fairer in my eyes...

andy katzelis

I agree, without a baseline (track times or other racers) how does one know how he stacks up. Everything in life, as well as race cars, is all about coutinuous measureable improvement. Anything less is a waste of one's time.

SAE hp is an equalization factor to compare different dynos results (I looked it up). But that still says the dyno was accurate or calibrated to begin with. And, if you read between the lines, SAE hp includes: full exhaust, accessories, and etc (and the date 1972) it was an attempt to more accurately represent what the consumer could expect from the powertrain and an attempt to reduce high insurance preimums for consumers buying sports cars. One should also consider the ramifications of the actions of the CARB, they were begining to ramp up at this point in time. SAE hp numbers are serious business; cars are sold and the big three is sued over these numbers.

On your eariler point, you see people (probably) daily who spend big money on parts that don't add any power. I see it all the time at the track. Now, imagine you're spending $5-10k on a "dynoed" engine that doesn't produce. Wow! Buyer beware.

There still needs to be a better way.

MaxRaceSoftware

What was the general outcome of the Hot Rod "Chassis Dyno" comparisons ???

94formulabz

Actually both STD hp and SAE hp are correction factors established by SAE. Actual or measured HP uncorrected is usually listed as 'actual HP' such as seen here: http://silver2kws6.tripod.com/images/dynosheet.JPG (copy and paste). Here is a sample of a STD hp data sheet and you can see it lists a correction factor of 1.04.

'SAE hp' refers to a modified version of the SAE J1349 standard of June 1990. Power is corrected to reference conditions of 29.23 InHg (99 kPa) of dry air and 77 F (25°C).

STP (also called STD) standard is another power correction standard determined by the SAE. This standard has been stable for a long time and is widely used in the performance industry. Power is corrected to reference conditions of 29.92 InHg (103.3 kPa) of dry air and 60 F (15.5°C). Because the reference conditions include higher pressure and cooler air than the SAE standard, these corrected power numbers will always be about 4 % higher than the SAE power numbers.

http://www.superflow.com/support/cyc...heory.html#CWP That page also shows you the actual formulas.

-brent

SageofKnight

I've been saying it for a long time. The dyno was never meant to be the track, it's a tuning tool. You can't really compare numbers with other people unless you both use the same testing methods.

If you are one of the people who ice down everything, use nitrous to supercool parts, and change setups you normally wouldn't just to get nice peak numbers then you are wasting a very good tool. Things like this are the reason you should be careful when reading claims, as you don't know what the testing methods were.

With that said, each dyno session should be done exactly the same as your others with only the changes in question being different.

This is one of the main reasons many Supras have a "Dyno Queen" stigma, as the little dyno tricks have a greater effect on FI cars.

robss96dcm

Not to beat a dead horse but I scanned and posted it here.

http://briefcase.yahoo.com/bc/robss9...dir=/My+Photos

91Z-28

Link doesn't work.

robss96dcm

Link is good, its just been hammered. over 200 hits since yesterday so yahoo shut off the tap. Just ck back when you get a chance and it should be good.

Denny McLain

Something very important that most people miss is putting too much emphasis on peak numbers. Peak numbers are a good indicator, but also is distribution of power. In other words…….. the curve of the powerband.

My last combination made 445rwhp and the current is 472. less than a 30 hp gain if you just look at peak numbers. However, at 7000 rpm I’m up 100 rwhp and the car is .35 seconds quick accelerating on the dyno from 5200 rpm to 7000 rpm.

A buddy of mine has a F-stock F body that runs very low 11’s. I’ll not tell his secrets but the peak power was way below what you would think a low 11 NA car would be. But the powerband went forever and was amazingly flat.

“Average hp within intended rpm range”………. My hero, John Lingenfelter

91Z-28

John beat that dead horse over and over. I remember when I read his SBC book he pretty much brings it up again in every chapter even though he covered it thoroughly in Chapter 1.