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Highest Numbers for NA Stroker?


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One of the big issues is that there are no SAE standards for chassis dyno setup' date=' operation, measurement, and correction. Without those standards there is no way to compare numbers generated from on chassis dyno to another or from one day's testing to another on the same chassis dyno.

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Dynojets have an SAE correction plus STD, DIN, and EEC. Comparing different brands can vary like Mustang vs Dynojet.

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can we all agree that the 1/4 mile dyno will always give you the least possible horsepower number? (granted you didnt make the best pass possible for 60 ft times, etc)

No, we can't. First there is this thread, which really is pretty shocking - 300hp discrepancy between 1/4 mph and dyno: http://forums.hybridz.org/showthread.php?t=107745

 

Then there is my engine, which at 8.3:1 compression with a badly slipping clutch turned 108mph according to a Gtech, at a not so speedy 15.5 seconds. I understand they read about 3 mph high, but cut it down to 105 and figure the weight I had in the car (me and a friend) and you're looking at 2635 lbs, so roughly 240whp. I just don't buy it. I'd buy that number for my new engine with 11:1 and a lot more port work, but for that first engine it just doesn't seem right.

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No' date=' we can't. First there is this thread, which really is pretty shocking - 300hp discrepancy between 1/4 mph and dyno: http://forums.hybridz.org/showthread.php?t=107745

 

Then there is my engine, which at 8.3:1 compression with a badly slipping clutch turned 108mph according to a Gtech, at a not so speedy 15.5 seconds. I understand they read about 3 mph high, but cut it down to 105 and figure the weight I had in the car (me and a friend) and you're looking at 2635 lbs, so roughly 240whp. I just don't buy it. I'd buy that number for my new engine with 11:1 and a lot more port work, but for that first engine it just doesn't seem right.

 

Wow that is a big diff, I stand corrected and more confused :redface:

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Dynojets have an SAE correction plus STD, DIN, and EEC.

 

Well, I'm a SAE member and I just searched their list of power measurement standards and there is nothing that I can find that references chassis dyno power testing for automobiles. There are standards (like J1349 for automobile engines) that cover all aspects of measuring power on an engine dyno for things like:

 

Gas Turbines

Commercial Diesel

Rotary Engines

Rotary Snow Plow Power Units

Gas Turboprops

Agricutural Tractor Power

Hydraulic Brake Power Rating

Hydraulic Motors

 

The closest I've found are the following:

 

Document Number: J2177

Date Published: April 1992

 

Title: - Chassis Dynamometer Test Procedure-Heavy-Duty Road Vehicles

 

Issuing Committee:

Heavy Duty and Commercial Duty Vehicle Performance Committee

 

Scope:

This SAE Recommended Practice has been adopted by SAE to specify: a. A standard procedure for chassis dynamometer testing of heavy-duty road vehicles for the purpose of determining power delivered through the drive tires.b. A method of correcting observed power to reference test conditions.c. A method of analyzing the test data to determine if the test results are within expected power ranges.This document is applicable to DOT Class 6, 7, and 8 and on and on/off highway heavy-duty road vehicles equiped with compression ignition engines, manual or automatic transmissions, and single or tandem rear drive axles.

 

Document Number: J2264

Date Published: April 1995

 

Title: Chassis Dynamometer Simulation of Road Load Using Coastdown Techniques

 

Issuing Committee:

Light Duty Vehicle Performance And Economy Measure Committee

 

Scope:

This procedure covers two-wheel drive vehicle operation and single-axle electric dynamometer load coefficient adjustment to simulate track road load within the speed range of track testing and the dynamometer inertia and road load simulation capabilities.The purpose is to provide a uniform procedure for adjusting an electric chassis roll dynamometer to provide accurate simulation of the resistance which must be overcome by the vehicle powertrain to maintain steady speed on a flat road, as determined by track coastdown tests on that vehicle.

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briann, ballpark figure on the asking price on your car?

15K for whole car, but he wants to actually sell the engine and go with a supercharged LS1, so we might just sell the engine.

 

We have the original hood, cv axles with modern motorsports billet adapters ready to install, extra 5 speed tranny and YZ rear flares (3" wider than stock) we just bought this week from Reaction Research.

 

quite a few pictures and information on our website: http://www.bbgraphics1.com

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  • 1 month later...
  • Administrators
Question on strokers. Is it possible to a working engine if you have a stroker setup with a maxima head?

 

Stoker L-series with flat tops and MN-47, sure, it would be a Race or Av gas engine only. If you wanted a pump gas stroker L-series with the MN-47 you will need custom pistons manufactured with a dish CNC’d directly under the chamber for a streetable compression ratio friendly with pump gas. This is totally do-able, the question then becomes, how large is the budget for your stroker MN-47 engine build?….

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I can rip off 2 dyno runs, 30 seconds apart and give you numbers and graphs that vary by more than 100%. Is the dyno wrong? No. The point is that those numbers can only be used for comparison against themselves, and you are only as accurrate as your dyno operator is trustworthy and accurate...

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  • 1 year later...
Does the fact that Tony got 286 whp at 14:1 and John Coffey got 287 whp at 13.5:1 make you wonder about your 278whp at 9.5:1 Brian? Cause it makes me wonder...

Can I quote you for "There's no replacement for displacement?" That doesn't end in "except for compression."

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Can I quote you for "There's no replacement for displacement?" That doesn't end in "except for compression."

I'm not really understanding what you're talking about. The point to the bit that you quoted was that I found it hard to believe that John's Sunbelt motor with higher compression and the same displacement as Brian's engine with relatively low compression put out roughly the same power.

 

You can quote me this time: Different dynos will yield different power numbers, so take them with a grain of salt. Put two cars on the same dyno one right after the other and then you can compare the results. Everything else is peeing up a rope.

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Eventually with cam changes, that same engine was dynoed up as high as 315 to the rear wheels just below 8300rpms. Blowing by like an SOB with .080" scores in the cylinders. It was non-stroker. But it's not a streetable engine by any stretch. Though with the EFI it was a seriously low idler compared to carbs. That was L28 bored 0.040"...

The 2L is a bit disapointing, as it is only around 11:1, and is only making 195-205HP to the rear wheels....at 8780 rpm. Exact same head we used on the L28, huge combustion chambers hence the lower compression. The engine is pretty much useless below 6000 rpm. After that it pulls decently. We were hoping for 1/3 less HP from the engine, so the difference between 14.5:1 and roughly 11:1 is around 8% (if it was making power at the same rate as a 320HP engine, it should be around 211HP instead of 195...) So that could be attributed to the lower compression as everything else is the same. We were hoping for around 215HP, so we may do a head specific to the L20A in this off season, either E30 or E31 with welded chambers. Equivalent CR as the 2.8 engine, and maybe some other tricks thrown in for friction reduction in the smaller, higher-revving engine.

 

With the strokers, I makes sense to me that they will make more power at lower rpms, with more useable torque band. A turbo would really help in 'useable HP and torque'---it's interesting to watch the dyno numbers on JeffP's engine develop as any throttle opening at almost any rpm produces 2-3psi of 'scavenging' boost...and MAN does that bump the torque up! Even at 1700-2000 rpms.

 

Incidentally, the Mustang Dyno has some really nice documentation regarding back-calculating power read on their dyno to SAE specs. Their operations manual is available for download as a PDF online, and it really explains how their dyno works. Made interpreting what I was seeing during a run much more relevant. I could look for peaks in the performance, backcalculate where they occurred, and then to relay them to Jeff for AFR or other corrections. I have noticed the Dynojets differ significantly from what the Mustag gives as readings. And since we have background stored on both dynos, comparison seems to be closer on the Mustang with their software package as well.

 

Neither dyno particularly likes a waste-spark system either...

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