boxer on a dyno

No worries. You will be measuring the HP at the wheels, so it will be a correct reading regardless of the gear you use. hp= torque x rpm/5252. In a high gear you have low torque but high rpm and in a low gear you have high torque but low rpm, exactly proportional to the gear you select.....there is no way to cheat or fool the dyno with gear selection

The magic of 1:1 on a us car is the output shaft locks to the input shaft eliminating the input shaft to countershaft and counter shaft to optput shaft gear losses....so you get a number that is a few % higher. In the ferrari trans, you alway go though 1 gear set so the output will be very close regarless of which gear you select. They still say go as close to 1:1 though because because gear losses are minimized when the 2 gears are as close as possible to the same size, but it doesn't make a very big difference on any car I've ever seen run.

A bigger factor is the mixture and timing. If you have plenty of timing and a rich mixture, you should see higher numbers the lower gears than the higher ones and if you are a bit lean with modest timing the high gears will look better.

Have fun!

What brand dyno will you be using?

 

i hope it makes more power than 270 hp at the rear wheel.

 

Very curious to hear your results. You may know this, I heard that recent calibration of the dyno is important to get a true reading.

 

Hi Pete,

Was that your Boxer's dyno results?

I was disappointed in my dyno run a few years ago too.
http://www.youtube.com/watch?v=jJKpH63nd94

261HP / 284 torque.

The shop has since installed a brand new dyno, so I will probably
do another run this spring after my major service (timing belts, etc.) is completed this winter. Plus I'm installing a different exhaust system too.

We'll see if the new dialed in cam timing/valve adjust and exhaust make a difference.

 

Gary,

yes, i dyno jetted out @ 270hp about 5 years ago. i was also sad at the result and was actually a bit ashamed as it was done at a nascar shop and they were all looking for big numbers.

now, my numbers came in at approx 20% driveline loss from the starting figure of 340 hp. i was close to the 18% rule of thumb but was told to consider that on a dyno jet "barrel" style dyno...there is additional loss at the tires if they are not in good or "gumball" condition. TRX's are NOT ideal tires for a dyno jet.

i have seen this first hand when testing my race motorcycles. the dyno tuner always told me to bring fairly fresh tires on the bikes as that would tell a better and truer tale.

just a thought.

pcb

 

Paul,

Where did you go ? I wouldnt mind going myself and see whats going on for my cars.

How much ?

Thanks.

 

Paul,
Is the timing adjustable on your car? When the 308s got CIS, they got digiplex ignition with no adjustments possible.

Your number in probably a touch low with tuning as you say....but ferrari's number is probably a touch high too

Over-all, the graph looks nice, the A/F looks pretty good too.

I think your right to be thinking cams. I don't know the boxer numbers, but on the 308s, the emissions 2V cams are something like 20 degrees less duration and .060 less lift than the early cam and are about exactly the same as the QV cams.....and they work pretty well with a little 29mm valve, but with a big 42mm valve, the valve never opens enough for the valve circumference flow area to even equal the seat flow area, so the intake valve is in the way and restricting flow always.

I’d bet that if you drop in the early cams you’ll pick up 20hp….but your ideal will be pretty poor until you do the EFI conversion and pick up another 10-20 hp. I’m thinking 311rwhp when you’re all done, let the wagering begin

 

its not that i need it...cause i know for sure the tr is pulling 390hp, and the plastic is 250hp ...it was just to get it in writing

BTW : Nobody has ever been nicer to you around here more than me you putz

 

You can make any graph you want in excel

 

its all hear say until we do the test. Would like to find out though...but since you wont tell me where, i guess you'll never know

ROLMAO !!! Thats true !

 

Paul,
Do you have the specs your cam and the 365? Lift and duration at .050" lift is best, but I can work with whateven duration number you have. If I assume your heads flow about what the 2v 308s do (unless you know flow numbers), I can plug it into the simulator software I have and see what the computer thinks will happen.

 

Ok, those are the same cams as early and late 308 the best I can tell.

There is always a little fudging to figure out what style to call the intake and exhaust, but I get

now....340 at 5700
with cams 360 at 6000
with an ITB set-up 414 at 6500....which seems optimistic with stock heads, but says freeing up the intake is agood think.

Now that you have a baseline, I could go back in an limit the intake flow unless I get the hp to match the dyno run. I didn't do that just yet based on your feeling that tuning might bring you the missing 20.

 

I think you are going to have trouble with idle...a lot of trouble and you'll end up cranking the idle sped up to about 1500 rpm. I'm pretty sure that ferrari and bosche spent a lot of time trying to set up the system back in the day and if they could have run more cam they would have rather than go to 4v heads. As I mentioned earlier, the 4v cams are exactly the same as the cis 2v cams..so it seems like they came to the conclusion that they were stuck with that cam grind and they had to deal with it.

One thing I noticed on the flow bench testing the QV stuff was that everything was matched pretty well one the CIS was out of the way. The manifold became the restriction instantly once the head was touched. The other thing is that typical of race engine up through the 70 and I guess even into the 80s, the exhaust flow was way to high proportionally to the intake and the exhaust port itself was about 50% bigger than I would like to see it. The boxster’s “bad” exhaust port may not be a problem at all for you.

Last, next time you go to the dyno, start the pull at 1000 to 1500. Speed shops like to start the pulls up at 50% of redline which is above where most people do most of there driving. I think they do it because a lot of hotrod stuff makes more top end but messes up the bottom end and they don’t want anyone to know, but that is where you spend 99% of your time so it good to know what’s going on down there particularly if you will be increasing cam duration.

 

Here's what I got for stock and then 365 cams with ITB. The torque cure is definately flatter on the stock engine, at least the way I set the model up. I computer tends to have more trouble getting the lower rpm stuff right, like the sharp turn in the in the touque at 2000 rpm on both graphs and the torque dip in the ITB graph at 3000 I don't believe are real. Both graphs should be smoother than the computer says.
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Paul, a 512bbi runs 14.1 seconds in the 400m(basically the quarter). The car is 3400 pounds, those numbers make sense. A carb bb may make 340 hp (din euro rating).