I found it difficult to accurately choose a replacement crate engine for my 68 vert.

Advertised HP numbers and dyno charts from a lot of suppliers appear to be simply computer simulations ....

Dyno results vary far too much from one tuner to another, and also from one test day to another. There are so many variables that can sway the results. tyre size and pressure and how hard the rear is pulled down onto the dyno can cause significant variatons. There's corrections which should be applied for ambient conditions... the placement of the air temp sensor can make a difference too.

A tuner that provides a big number leaves his customer happy.
A tuner that provides a low number (although it is probably more accurate in absolute terms) will probably be cursed by the customer.

A dyno is a tuning tool.... only compare your before and after numbers to assess what the improvement is with any mod.

In my opinion, the real assessment of actual engine power (imho) is the performance at the strip....
The mph at the end of the 1/4 mile is probably one of the best indicators of effective horsepower.

If you can't get to a track, the use of a G-tech meter can provide some reasonably good data to assess effective hp if used properly.

cheers

tom

PS.... I chose a motor which I hope will get me into the 12's.... a 383 rated at 460hp. Once it's installed and run in, I'll put it on a dyno and compare the actual numbers to the claimed rating....
I'm hoping I'll get around 320 rwhp with a TH400 trans....

 

I dont care how much HP you have, it`s got to get to the ground. To much HP and you could go up in smoke, not enough HP, well thats self explanitory. You normally lose unless the other guy breaks.

I too have been a mite skeptical of some of those HP dreams and quotations! But on the other hand it`s probably best to not call anyone as in playing poker. Not everyone here is a racer but most of us can quietly dream on. Right!

 

I like the remarks made by car owners at car cruises when asking a simple question about their engine. "You know this engine came out of a corvette." As if GM had a special factory building only Corvette engines. It's a Chevy Stupid.

Or, "Yeah, it's bored out...... 30 over." BFD


I blame Bush & Cheney for the HP discrepencies.

 

If this is what tweaks your peepee use an eddy flow dyno.

 

Though I will probably never put my car on a dyno, I do use one extensively on my drag bike. I use the same dyno, same tech every time. We try to tune in consistant weather conditions. We do not always tune for the most horsepower and torque, but the smoothest and the most consistant power curve. From tune to tune, we may have to bump the air bleed, intermediate or main jet ,change a Thunder Jet, a timing change of one degree, plus or minus, or even so much as a minor plug gap change. From one tune to the other, horse power and torque never changes more than one or two percent.
I'm not an expert on dyno tuning. That's why I hire a tech to do it. Numbers can change for different reasons, even tires. You'll get higher readings on street tires than drag slicks, due to the patch contacting the ground. This can go on and on. Dyno's are what you get out of it, and is open to interpretation.
The old 96" ironhead has 146 RWHP and 182 FTLB torque @7755 RPM. It will rip your arms off! And it is obsolete.

 

The non Chevy guys said Chevy engines were under rated. Maybe theirs were too over rated.

According to Ford, they took the 360HP 390 C.I. Thunderbird engine increased to 428 C.I., etc. & lost hp to 335.


This was obvious when they came out to me.

 

In my opinion dyno simulators are also a very good tool to help design an engine to do what you want. Some guys want all there power at the upper RPMs and go for maximun power out of a given build, Drag racing. Some want a streetable combination with a flat torque curve but still pull as much power out of you combination of parts as possible. The dyno simulators help the engine builder put together a good combination of parts that compliment each other for the intended use. Without them you are just guessing at what will work best for your use. In the old days you built the motor, ran it. If you didn't like the performance you bought a new cam, or a new carb or new heads, changed them out seen how it worked after you dialed it all in. No improvement change somthing else. The #'s here DO MATTER because the computer simulation will give you information you can use to build what works for you without all the old school trial and error. Most of the good simulators are also very accurate.

 

Story:

C5 owner - I have 500 HP after all my mods.
me - Wow, so you had it on a dyno?
C5 owner - no
me -

 

It's all their fault.

 

Don't know that I need to know the numbers, or want to for that matter.

1977 L48 LOL

I don't need to know how low the numbers are. I don't need a dyno to prove my upgrades, I feel them seat of the pants!! A little more go-fast foot pressure, oh yeah, that works.. Feel the difference!

The only numbers I need are:
How many hours to complete this job?
How many jobs to complete this project?

Ask about my girl? ... my vette.
Scale of 1 to 10 ? You bet, she's a 10!

See even those numbers become questionable?

 

Very typical. I had a Z0-6 owner a few years back that wanted to race top speed or one mile drag race for any amount of money against my old beat up 79 equiped with a solid roller 383.

I should have been a heartless bastard and taken him for more than just a few hundred dollars

 

Well... I've got 1 million CRANK horsepower.

so eat that.

 

That anything like Reaganomics?

 

I say as long as your car feels fast your good. I feel my car hauls and it runs 12.9. Maybe 12.8 now after lightening it up some.

I have slicks so I have no tire spin on acceleration.

 

dyno numbers mean nothing to me.. I care for track results.. I don't care if I have 800 or 950 HP when I'll be hitting 8's in the 1/4 mile..

 

These measurements are *very* useful for people wanting to compare engines, or to assess the effect of changes made to an engine.


Maybe, but you need tons of additional information to use the numbers for a comparison unless you are comparing identical cars. Example: What's faster - an H1 with 550 rwhp or a Lotus Elise with 450 rwhp?? The Hummer because it has more rwhp, right?

Rear wheel dynos are useful for comparing changes made to the rwhp from both engine and drive train.

 

forget total hp .torque is what matters i have a 325 hp motor with 375 ft lbs of torque and i smoke mustang gt,s every day i also have mono rear spring and mono coils and steeroids rack....sorry mustang boys...save the wave

 

i am not sure how accurate the sims are in real world running hp numbers but they do help with design. (i kind of do hope they are close though.) also the dyno can help out a lot with tuning a car, getting it dialed in faster, and knowing the change in rwhp before and after a mod or change in tuning. as for being accurate the only way to know how much usable power a car has is to take it to the track and see. my z has more power than traction when running on street tires. i have to manage the power output by adjusting the amount of right foot travel. each dyno is dif. some are generous and some are slight with the numbers. the numbers are only a ballpark estimate used for building, tuning, and bench racing. the first two are important. the real and only accurate numbers are on a time slip.

 

lotsa people walking-around with a chubb in their pants over dyno-numbers, but no-clue how the car would perform at the strip.

 

I disagree