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Dyno Results: 4.0 OHV

majorlag

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July 31, 2002
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City, State
Knoxville, TN
Year, Model & Trim Level
1994 XLT 4x4
Hey guys!

Just wanted to post some info for anyone with questions about horsepower/torque gains from bolt-on engine mods and chip upgrades. This past weekend I had my Ex dyno tested with an air-fuel ratio check (just to satisfy my gnawing doubt). This is an original 4.0 OHV with 98k+ on it, no towing, pretty regular maintenence, with a fairly new rear main seal (long story). Otherwise, tip-top shape. Stock numbers at the flywheel were 160 HP @ 4200 RPM and 220 FT-LB @ 3000 RPM. With assumed drivetrain losses of about 30% (25% for auto tranny and 5%? for transfer case and diffs), this leaves 112 HP and 154 FT-LB.

My mods include (see sig at bottom):

63mm TB
70mm MAS
Apten 93 Performance Chip
KKM Intake
Flowmaster exhaust
4.10 Gears

Results (at the wheels):

127 RWHP @ 4200 RPM (approx. 181 HP at flywheel)
200 FT-LB @ 2700 RPM (approx. 285 FT-LB at flywheel)

My approximations are based purely on assumed 30% losses and do not reflect actual calculations. Also, the shop had never tested an Ex before and had some difficulty, so some pulls were performed in 1st or 2nd gear only and some were in drive.

Conclusion:
All my modifications cost about $1500 :eek:, so that's about $71/HP or $17/FT-LB. Not very cost-effective. Superchargers run about $3500 (assuming professional installation), and may yield 80ish HP, or $43/HP. This requires, however, a big pile of cash at one time, which is why I didn't go that route.

Measureable numbers may not be that impressive, but the perceived power and improved driveability are very noticeably. I am pleased with the results, and would recommend these or similar modifications.
 



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Good info, thanks for the post.
 






One ought to consider how bolt-ons significantly improve your power:weight ratio. They are light, and add a few HP here and there. If you add 45 hp in 6-7 pounds, you are definatly going to feel the difference. I think that is the main reason between discrepancies between what one "feels" is different and what a dyno "shows" as the real gains.

None the less, nice Dyno #s for a 94 OHV. I'm not sure your HP measurement is accurate though, it seems unusually distant from your torque measurement.
 






Good to see some dyno num,bers up here. can you post the sheet? Was this on a dynojet
 






Getting a dyno in our motorsports shop in about a week. Employees get all the dynos they want :)p), so I'll get some of my V6 SOHC here soon, should be interesting.
 






DYNOJET Sheet

Here's a copy of the sheet they gave me. They didn't record the entire RPM range, apparently. I'm trying to get them to email me the data file so I can use DynoJet's free viewer. And maybe print out a better copy than this one!
 

Attachments

  • dynoj test.jpg
    dynoj test.jpg
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First let me point out one thing: See how smooth the lines are? Quick variations in a dyno chart are due to ignition problems and most vehicles have slight hiccups even stock. Our X's don't, this is why I don't recommend ignition mods ;)

Most people get about 120 rwhp stock, so you actually got less gains :(

However, while you may have only gained 7 peak hp, you may have gained much more at other places in the RPM band. Peak hp is nothing, it's how flat your power curves are, with a slightly gaining, flat power curve the best.

You need to test in 3rd gear to be totally accurate (1:1 gear) but looks good. Explorer = low end torque ;) You gained a shoot-load!
 






Very interesting, especially the torque. After all, that's what is felt in everyday driving. Looks like it peaks at a low rpm also.

Majorlag, what mod would you say gave the best results? Possibly the free-flowing exhaust?
 






Your results are very typical for the OHV 4.0L.

It would be interesting to see a N/A 4.0L that has had the heads and camshaft done on top of your mods, thats when the OHV wakes up.
Of course NOS and a SC are your best bang for the buck. :)
 






410Fortune said:
Of course NOS and a SC are your best bang for the buck. :)

Of course! :bounce:
 






This probably sounds dumb, but I have no idea how to read that above chart. Considering the top box, is the top line torque and the bottom line HP? Am I correct in assuming (that is, if the lines corresspond with what I just said) that as I read the lines to the right and the RPM's climb, the HP climbs as the torque diminishes?
 






That is what happens in most vehicles, moreso with trucks. HP climbs with RPM and usually peaks around redline or 400-800 below, and torque drops after it's peak midway through the powerband.

HP is just a function of RPM and torque, which is why it usually keeps climbing. And the key with torque isn't really the peak #, but the "area under the curve".
 






I thought tourqe and HP pretty much hand in hand. I knew Torque fell off quicker than HP, but I didn't know that it a reverse curve opposed to the HP curve.

Interesting, thanks.
 






Most effective mods

The modifications that made the most significant effect on perceived power were (most change to least change):

4.10 Gears!
Apten Chip
TBI and MAS (installed together)
KKM Intake
Exhaust

I know that the chip, without the other mods, will not make as dramatic a difference. In my case, the chip really opened up the higher RPM ranges (above 3000). I find that the transmission doesn't always downshift when it would before, like trying to accelerate on the Interstate in OD. With my 3.27s and before the TBI and MAS, I could not accelerate in OD above 55mph. The torque converter would have to unlock or the transmission would downshift. After the TBI and MAS, I was able to accelerate some and maintain speed going up hills. The gearing made the biggest difference--it was night and day. For someone looking for a "zippier" Explorer, that's where I'd recommend starting, if you don't mind lower gas mileage!

;)
 






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