thingo

I presume they were measured using a similar technique, but since they were not even done in the same state you could always nitpick a difference to support one viewpoint over another, the numbers in each case were measured to show before and after, so valid in that respect, I just use them as a guideline.ymmv

Rogue_Ant

Yet another staw-man argument.
And besides the point that Bandimere is one of the premiere 1/4mi tracks in the country, and set the standard for all the big-boy tracks.

Exactly what benefit are you adding to this thread?

refresh951

Thanks Sid. Please send it over. Would love to test it. I will pm you.

Really appreciate you posting the numbers. If you can get a few specifics about how they were tested the data could really be useful. Any chance you can call the shops that did the testing?

thingo

Shawn, as I said, I don't think you can really gain any proper meaningful data by comparing the two figures, it is like comparing different dynos, but that said the intake test specifies 28" WC. I just use the numbers for tuning.

refresh951

Thanks!

Thom

I would argue that a standing start puts a lot of strain on the drivetrain, meaning that off-the-line performance may depend nearly as much on the ability of the drivetrain/suspension/wheels/tires to put the power down as on just the engine power itself.
By using acceleration times from a launched start at a relatively high speed, we significantly reduce the risk to lose traction.

This is the measurement of wheel horsepower, not engine horsepower, which I think is most relevant in the discussion and what we are all interested in.

Thom

Was the head you had flown a regular 8V head or a 2.7 head?
The larger intake ports on the 2.7 head may not be correctly exploited if used with a stock 951 intake that's got smaller intake runners.

Sorry Shawn, we are derailing your thread again Any planned date for the initial start up?

333pg333

That's the problem with comparing flow rates as I've seen them. Too many with such differences. Just like dyno numbers on like for like mods.

The acceleration runs from a roll might be the best option although I've never ceased to be amazed at how little difference the start makes to the ultimate mph at the end of a standing 1/4...but this seems verifiable 24/7.

Paulyy

There's always altitude though. That'll change numbers.


I figured (i have already tried this) you can work out your acceleration graph and see where you've got the most power if you graph the time the rpm goes in 100 rpm increments as a line graph, you'll get a good idea in how your car accelerates.

blown 944

Absolutely it adds stress to the drivetrain, if you push it. My point is, like I've said in the past, you can take off just like you would from a light and the mph will be very close. Ie; there is enough distance to make up for it. I have logs of taking off at 1200 rpms and the mph wass close to the previous run at 4500.

I have no doubt that a rolling start may be able to give a hp number. Again, there are variables, such as shifting times, aerodynamics. So no method is perfect to attain rwhp. That brings me to your next question/comment.

I am talking about rwhp. The normal process is to add drivetrain loss, or vise a vs if on an engine dyno.

This method has been tested for decades now.. Ex; we would put an engine on the dyno, get the number (x) subtract drivetrain loss (y) use the final figure along with the weight of the car. Using this, we had a pretty accurate idea of what mph the car would run. So if you reverse that process, you can gather rwhp and fwhp.

I don't really understand why this method is being so disputed. It has been around for as long as I can remember.

If its about what my hp is/was, then forget my numbers. I don't care. All I was looking for was what mph the car could do. As I still do, it gives me an idea of what cars I can compete against (outside of the 944).

Sorry for the OT.

Thom

I agree 100% that acceleration times should matter more than HP figures, this is why I was asking about your 100-200 and 100-150 kph times with your 522hp motor. I am not too satisfied with rwhp figures either because there still seems to be a lot variance as to how dyno operators apply the correction factor (and the usual other factors, but let's try not to rehash this on here).

Another point is that it is rather difficult to reproduce on a chassis dyno the vacuum effect of air flowing around the bodywork, which helps extract the air coming out of the engine bay from below (and above, when using hood vents). Placing a huge fan in front of the car is better than nothing, but that air is not helped being extracted, and the IC needs proper extraction to avoid being heatsoaked after a handful of runs. This affects the reproductivity of engine performance and puts limits to a chassis dyno as a measuring/tuning tool on intercooled engines.

In fact the 100-150 kph (62-93 mph) time should be the easiest to measure as it corresponds to going from 4000 rpm to 6000 rpm in 3rd gear on the stock gearing (and with the stock 245/45 16 tire size, but any other tire size is easy to calculate from). Maybe you have it logged already on your 1/4 mile runs? That would give me some meat to chew on apart from your 1/4 mile time

refresh951

First off I do not mind OT as long as it is respectful dialog, so no problem. Also, this really is not OT as it is useful to me in that I want to understand the limitations of the stock intake.

Second, IIRC the only reason you went to the dyno was because many doubted your HP claims. Your dyno fully supports your 1/4 mile hp claims and is very consistent with you 1/4 mile formula. Again, you proved it with real world results both ways.

My main point is that I am convinced you were running over 500 rwhp and you did it with a slightly modified intake. You also are not the only one who produced over 500 rwhp with the stock intake. This is significant to me because either a custom intake or an extrude honed intake are very expensive. I am going to make sure I really need to spend the money before I do it. Personally I do not think it will be necessary but I will find out soon enough.

blown 944

Thom, I will see if I can find some data.

Unfortunately, my logging laptop had a hard drive failure about a month ago. My logs were on it but much more important photos of my son were on there. So I have it at a recovery friend right now. I will for sure get the photos but I don't know what else he can retrieve. In the end the logs are minimal in comparison of importance.

Thom

That's ok Sid, I can certainly live without it.
I apologise for sounding like the sceptical guy, perhaps I should have my engine on the dyno to see it for myself. Getting past the 500hp mark with these "old" engines has always sounded like a fantasy to me, but maybe I already have the potential to get there too, I don't know.

Back on topic now!

blown 944

Thom, I can appreciate being sceptical. I am used to explaining things, even to my old drag racing friends. They have made the comments that "it's a different horsepower, isn't it?" their thoughts come from thinking about it from a "ET" point of view. As that is generally the first thing they look at. However, as cars have become more powerful and they are pushing close to 200 mph they are now understanding.

Here are a couple of examples of cars that I have owned or driven for comparison.

My Nova at one point ran consistent 10.50 @ 125mph without nitrous. This engine Dynod 630 fwhp. With the weight of the car and the losses of the automatic this proved to be a 500rwhp setup.

My brothers camaro ran 11.7 @ 121 on out last run. His car weighs quite a bit more (3800) and this calculated out to right around 540rwhp.

The point I'm tring to make is that, the horsepower is real. It requires a certain amount to get to the end of the track at a certain speed.

Believe me, coming from my background, I am still very surprised that this little engine can make as much as my old 406ci and as much as my brothers 415 on a little nitrous.

Now, if I could just get the ET.....