Jensen Healey on the Dyno - Results Inside

Jensen Horsepower

  • 111-120

    Votes: 0 0.0%

  • 121-130

    Votes: 0 0.0%

  • 131-135

    Votes: 0 0.0%

  • 136-140

    Votes: 0 0.0%

  • 141-145

    Votes: 1 100.0%

  • 146-150

    Votes: 0 0.0%

  • 151-155

    Votes: 0 0.0%

  • 156-160

    Votes: 0 0.0%

  • 161-165

    Votes: 0 0.0%

  • 170+

    Votes: 0 0.0%

  • It won't make any - it'll break!

    Votes: 0 0.0%
  • Total voters
    1
Ron Earp

Ron Earp

Administrator
Well, not yet, but they will be after Friday or Saturday. Promise.

However, we can have a little poll for entertainment. How much rear wheel horsepower do you think the Jensen 2L 4 valve motor will make on a dynojet dynometer? Motor is built to IT specs, 0.5 compression hike, 0.030 over, port matched, carbs worked over a bit, 4 into 1 header with 2.5" exhaust through not much of a muffler. Motor will be run to about 7000 RPM, no more on the dyno.
 
I like that 161-165 vote, be nice if that happened!

I am not sure a 140 rated stock flywheel 70s era motor can put out that sort of power, but I can hope!

R
 
Hey Ron,

Is that measured hp at the wheel or on the crank? I assumed by your comment you were talking about crank hp; but, the bi-modal distribution seems to indicate a 50/50 split between crank and wheel hp people.

James
 
Hey James,

Question is how much rear wheel horsepower it'll put out.

The stock/flywheel rating comment is just to give you the baseline from where the motor started from. I'd suspect the untouched stock JH motor would struggle to put down 110 rear wheel hp from the stock 140 flywheel hp. So, the folks that voted that she'd make 160+ rwhp are counting on a big increase!

Nonetheless, it is possible to see some large gains. Jeff's TR8 was stock rated at 135 flywheel hp, and we now have that car putting down over 160 rear wheel hp, a big difference. If the JH were to see similar gains it'd see 165 rear wheel hp, but the JH motor is considerably more advanced than the TR8 motor in design, although it is rather ironic they both breathe through the exact same Stromberg carbs. Keeps our racing parts and spares to a minimum.

R
 
Hey James,

Question is how much rear wheel horsepower it'll put out.

The stock/flywheel rating comment is just to give you the baseline from where the motor started from. I'd suspect the untouched stock JH motor would struggle to put down 110 rear wheel hp from the stock 140 flywheel hp. So, the folks that voted that she'd make 160+ rwhp are counting on a big increase!

Nonetheless, it is possible to see some large gains. Jeff's TR8 was stock rated at 135 flywheel hp, and we now have that car putting down over 160 rear wheel hp, a big difference. If the JH were to see similar gains it'd see 165 rear wheel hp, but the JH motor is considerably more advanced than the TR8 motor in design, although it is rather ironic they both breathe through the exact same Stromberg carbs. Keeps our racing parts and spares to a minimum.

R
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Hey Ron,

I wish I could change my vote then because I figured you were talking crank hp. I realize that your motor is more sophicated than Jeff's Aluminim V-8 but on the other hand there's no replacement for displacement especially in the rpm band being used in an IT car. To be kind I'd say 150-155hp would be the most anyone could expect, I was one of the 156-160hp'ers. Good luck, and I'll be watching to see your results.

James
 
I'm thinking around 140ish myself, although I'm open to being suprised. Hope I can get some time, so far I've struck out with the two shops, but I'll see if I can get a slot in the late afternoon today.
R
 
I put 20 lbs of rocks in the trunk the other night. You just didn't catch it. [/b]
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He will figure it out at the first corner! LOL....

(And maybe panic thinking the internals are becoming external...)
 
A box of rocks banging around in a metal box is basically how a Lotus 907 motor sounds anyway. He'll think it is normal.
 
Well, the results are in and not entirely disappointing. I'd say somewhat predictable to a certain extent.

Where I live I can't run the JH any because it makes too much noise and the neighbors complain. So, this first dyno run with this car was a true "discover the issues" sort of run. And we discovered them!

We found out we are not getting nearly enough advance out of the dizzy. Total advance was only like 28 degrees or so all in. Not good. And, we had some spark scatter as well every second or so on the dyno at speed that increased in frequency as the revs went up.

Worse than that was the A/F mixture. The car is running extremely rich with the front carb fueling 1/2 producing EGTs that are about 400F lower than 3/4. So, we're drowning the front two, and only soaking the back two. Either way you look at it we're far from optimal.

Above about 5000 RPM the dyno plot breaks up quite a bit and curves downward. The best peak hp recorded was about 118 rwhp, and about 120 ft/lb tq. Not too good, but about 20-25 hp off of where we need to be.

On the upside there is a lot of tuning and straightening out to do on the car and we think we can find that missing hp. Car still runs fine, idles decently, just doesn't pull too well once the tach swings by 5k. Exhaust gets hazy/gray, rich, and the motor feels lazy from that and timing.

So, back to the garage to do some work. I'm definitely titling this thing so I can legally drive it about. Some of these issues could be discovered in an empty parking lot or highway without disrupting the nice folks that live nearby without all that hassle to trailer to and from the dyno.

R
 
Maybe not, but if I can get one with no washer bottle, and I'm pretty sure I can, then I'm game! :D I wonder how long I can delay the DMV on inspection before they come to get me?

It has been very convienent driving the Miata back and forth to the alignment shop, that I do know!
 
You could do it as vintage, do not have to have it inspected that way. That is what I did with the Opel. You will get quite a bit of attn. if ya know what I mean. Make sure you have all your insurance and stuff together.
 
Sounds like you could use an egt gauge, or an O2 sensor for setting your mixture on the top end or you could always use the art of reading plugs. Also, if your running a DOHC type set up with the plug's centered, you won't need 32degrees of advance. My motor, for example, was set to 24* total advance we tried 26* and saw no difference, so it was set back. Get your carburetors jetted properly, and get back to the dyno.

James
 
118/120? It better sound a hell of a lot cooler than a Miata for all that work you're putting into it! (post sounds sounds will ya?) :biggrinsanta:
 
Sounds like you could use an egt gauge, or an O2 sensor for setting your mixture on the top end or you could always use the art of reading plugs.
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Actually, we have EGTs, two of them, and I have an O2 sensors. But like I said I can't drive the car around the neighborhood to even get some basic things checked such as that. EGTs at WOT of about 1200 and 900 are no good, but after a couple of pulls we were done. The Strombergs are not "fiddle friendly" on a dyno, they require a bit of work to change settings, thus there was little I could do beyond timing without running over our slot. Spark scatter/bad ignition is a big issue too and shows on the dyno graph (and timing gun) throughout the entire range.

The dizzy is the same one that you find on the MGs with a smaller cap to fit under the manifold. Our engine friend has a clear cap for these things and when installed on the dizzy with a MSD it looks like a fireworks display and not in a good way. Occassionally arcs will travel and hit three contacts on the dizzy at one time. I can switch to a later model dizzy (1975 cars) with a larger cap and it appears a few folks in JensenLand have had good experience with this. Also will have the dizzy worked over to correct a few issues with it that I've learned about when running the Petronix.

We also had a fuel pressure issue that showed up too, with the gauge dropping a couple of pounds below nominal. Adjusting the regulartor would get it back up, but once it creeped down again. So, need to check that out as it sure isn't helping.

We still learned a lot and one thing we learned is the car has potential. I figure the car was running about as bad as the TR8 did on this dyno once and it made 125hp. With proper fueling, spark, etc. we got it up to 160, so there is hope that we can get in the 140+ range that we need on the JH. Lots more to do, but we're doing!

And yep, it sounds a hell of a lot cooler than a Miata and looks a lot better to boot!!
 
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