Here is the engine dyno pull for my 1995 3.6 993 pre-vario ram motor currently inside Fritz. SirAndy has the exact same motor configuration that I sold to him. (I had 2 3.6 engines for a few weeks!)

Motor has stock ECU, with the stock air filter and box cut to allow more air flow. 1 3/4 inch headers with Phase 9's. No AC or PS pump. 100 Octane gas.

It is interesting to note that this motor was $7500 delivered to my door 2 years ago with 34K miles on it. I sold the 993 exhaust, the upper assorted hoses and engine tin for $700. The headers were ~$550, so I came in at 7350.

The dyno was performed by Jerry Woods and the figures have been corrected for altitude and humidity and whatever else is corrected:

RPM HP TQ
--------- ---------- ----------
2500 87.1 182.9
3000 112.4 196.7
3500 137.7 206.6
4000 172.2 226.0
4500 208.6 243.4
5000 246.1 258.4
5500 264.3 252.3
6000 287.6 251.7
6500 282.6 228.2

Pretty awesome torque curve. And you can feel it. Right now I have a shift light set at 6K. I remember Brad saying the shift point for acceleration is about 500 RPM past peak Torque....which makes my shift point between 5500 and 6000 RPM. Factory red line for the motor is 6800 RPM I believe.

SirAndy,

This is a good basis for you to start with your chip mods and air intake mods. 300+HP with a chip seems attainable. The headers used for this dyno pull are the ones I sold you.

If we didn't have to use a 915 box, this -6 conversion swap makes alot of sense. 288HP out of a non-stressed motor with hydraulic valves.

Nice!

Bill P.

QUOTE (nine14cats @ Feb 7 2006, 06:00 PM)

SirAndy, This is a good basis for you to start with your chip mods and air intake mods. 300+HP with a chip seems attainable. The headers used for this dyno pull are the ones I sold you.

schweet! yes, excatly what i was looking for ...

thank you sir!
Andy

QUOTE (nine14cats @ Feb 7 2006, 06:00 PM)

... I remember Brad saying the shift point for acceleration is about 500 RPM past peak Torque....

In theory, you want to shift where the power available to you in the new gear is equal to the power available in the old gear. So something like 500 RPM above peak power, not peak torque! If you shift before peak power, you will lose more acceleration by having to go through a taller gear than you gain by putting the motor close to its peak torque.

Remember, stock 914-4 makes peak torque at 3500 RPM. Why do we shift at 5000? Because that's peak power.

In a given gear, you accelerate the fastest when the engine is at its torque peak. But if you can choose a gear that runs the engine near its power peak, that will give you greater acceleration yet.

--DD

Bill,
I think your dyno chart bears out what we found at Laguna.
When I was shifting just before 6K the car pulled very nicely.
I don't think with the stock chip, changing your shift point is going to get you much since the HP and Torque begin to fall away above 5.5Krpm

Makes you wonder what it would be like with a little chip magic along with some intake mods

I'm looking at chips right now. I haven't decided on one yet but I'm starting to look. I have heard of a few folks having a switchable hi-performance chip. You can flip between stock and performance.

Jerry told me he doesn't think there is much to gain on air filters since he has dyno'd both a K&N cone and a stock paper element with the box cut to let more air in. No difference supposedly. I have to run 1 5/8 inch headers per my class, so only the chip is left, since class rules state I can't touch the intake system from plenum to engine.

But bone stock.....what a wonderful motor!

Bill P.

QUOTE (nine14cats @ Feb 7 2006, 07:00 PM)

It is interesting to note that this motor was $7500 delivered to my door 2 years ago with 34K miles on it. I sold the 993 exhaust, the upper assorted hoses and engine tin for $700. The headers were ~$550, so I came in at 7350.

Was that a one-off great deal or is that the going rate for a 3.6?

QUOTE (anthony @ Feb 7 2006, 09:42 PM)

Was that a one-off great deal or is that the going rate for a 3.6?

say what

QUOTE

QUOTE (anthony @ Feb 7 2006, 09:42 PM) Was that a one-off great deal or is that the going rate for a 3.6?

That is a great deal, the older they get the less chance of a low mile motor.
In the last year , and 1st in line , of at least 3 other people for each one
87 3.2 6200
86 3.2 40k 6400
86 3.2 48K 6200
86 3.2 70k rough 2700

Sorry no 3.6 values , Be ready to purchase , Timing is everything

Thanks for the info,


I've got the exact same setup,always wanted to have an idea what my 6 was packing.


great job Bill,


Ron

Sorry about the late reply guys, I'm in Montreal on business.

Over the last 24 months the 993 3.6's have gone up in price. I bought mine from LA dismantlers. The 2nd 3.6 I had came with another car I bought. I have been watching e-bay and calling the normal cast of recyclers (LA Dismantlers, ect.) and the lowest price I got was $8800 delivered to my door with a 60K+ mile motor.

Private deals are probably better, but on the bird board there hasn't been many 3.6's coming up for sale, and when they do, they want alot. There is currently a carbed 964 3.6 freshly rebuilt for $12K....

When I bough mine, I called around everyday for about 3 weeks. I found the motor and had it shipped. PMS had a 48K mile motor in stock that he was willing to off for under $8K. But this was 2 years ago. I believe the prices have gone up. If you purchased a sub 50K mile motor for less than $8K, you probably got a good deal.

Bill P.

Bill,

Where are you in Montreal ? I work right downtown, car for a bite of lunch tomorrow ?

Michel Richard

QUOTE (Dave_Darling @ Feb 7 2006, 09:30 PM)

QUOTE (nine14cats @ Feb 7 2006, 06:00 PM) ...  I remember Brad saying the shift point for acceleration is about 500 RPM past peak Torque.... In theory, you want to shift where the power available to you in the new gear is equal to the power available in the old gear. So something like 500 RPM above peak power, not peak torque! If you shift before peak power, you will lose more acceleration by having to go through a taller gear than you gain by putting the motor close to its peak torque. Remember, stock 914-4 makes peak torque at 3500 RPM. Why do we shift at 5000? Because that's peak power. In a given gear, you accelerate the fastest when the engine is at its torque peak. But if you can choose a gear that runs the engine near its power peak, that will give you greater acceleration yet. --DD

The best shift point is different for each gear as the RPM drop for each gear change is different. The best way to determine the shift point for max accleration is with a plotted gear chart (RPM & Speed) for your transmission.

The optimum shift point drops the engine rpm back to peak torque at the engine (not the wheels as gear ratios affect this). As per your dyno plot your peak torque is at 5000rpm, therefore each subsequent shift will need to drop your rpm to there. As you move up the gears you will be able to shift earlier ie not have to rev as high(generally).

Bill,
What tranny are you running again?

Patrick, I am sure his new racecar has a G50. Not to mention I checked the thread where he announced his aquisition of Fritz. Yes it is a G50
It shifted very nicely with no shifter slop....not like a 915

I have had Porsches with 901s (4 of them) One of those was connected to a 2.7RS motor
915 (1)
G50 (1)

The G50 is by far the best shifting of them all...period.

Problem is I have more money into a 901 (total rebuild, Guard 80/20 and billet int plate) than Bill has in his motor. Better to regear than sell and upgrade? Is a re-geared 901 so equipped as robust as a 915 or G50?

Sorry Bill,

Sorry Patrick,
my 914-6 with the 2.7rs motor had short 3rd 4th and 5th gears.
I rebuilt the tranny 4 times in 5 years. Car was AX/TT almost exclusively, motor had too much torque for the tranny. I ran turbo half shafts so the tranny was the weakest link.
Many folks have run big motors on 901s but my experience and that of some of my friends says that it will be rebuilt much more frequently.

Since you have a nicely built 901 I would at least give it a try. Just watch the low speed launches in 1st and 2nd.

If you really want to know your exact shift points you have to plot your accelerating torque for each gear vs car speed. The final plot will be a series of arches. First gear will have high torque and as the car speed increases the torque will drop off to a point where it crosses the torque of 2nd gear. That's your shift point. The same applies to to to the other gears. That way you always have to most accelerating torque for any speed your driving. The shift points will vary depending on the torque curve of the engine and the difference between gear ratios. Its hard to set a hard and fast rule. I did this for my formula vee back in 0t he 80's and it wanted to shift just before 6k. Its not hard to do once you have the dyno sheet you know all the other numbers: gear ratiios, final drive ratio, and tire size. Of course, you don't want to take it over redline.

have fun,
Bill

How is it that HP /torque threads seem to turn into
tranny discussions?

Not being one to fight the trend........

My solution is to lay in a stock of 901 bits.
My engine is no torque monster, but in combination with big tires, surely puts a lot of overstress on a 901 under the right circumstances.

A long discussion with a local guru filled in a few blanks on my 901 knowledge. He says that the 901 can take more abuse than is generally acknowledged with one exception: heat. Heat absolutely destroys 901s.. end to end, says he and it's "worst condition" in a 914. Since I don't track my shitbox, heat is not a big issue. I have spares to cover the most common torque related issues, so I'll continue with the 901.....the expense of all was considerably less than the cost of a Wevo kit for a 915.

QUOTE (Sideways @ Feb 9 2006, 06:39 PM)

The optimum shift point drops the engine rpm back to peak torque at the engine (not the wheels as gear ratios affect this). As per your dyno plot your peak torque is at 5000rpm...

Not universally true. As I said before, the optimum shift point is past the peak power rating by enough that the power in the new gear's RPM is the same as the power in the old gear's RPM. The exact RPM that you hit peak torque is irrelevant. (This assumes that it takes zero time to shift gears, which is very much not true, but accomodating that in the calculations is beyond me at this point.)

Due to the way the gears are spaced, you want to shift a little higher in the lower gears and a little lower in the higher gears. But all of your shifting should be done somewhere between 5000 RPM and redine (remember, stock 914 motor, not the one from the dyno graph posted earlier in this thread!).

With the dyno numbers posted earlier, I would shift at redline. The power peak appears to be somewhere above the RPMs achieved in the dyno run, which presumably went up to the redline. If you shift at peak torque, or shift to get to peak torque, someone shifting around the power peak will walk away from you. They'll gain more from the lower gearing than they'll lose from the engine making less torque.

--DD

QUOTE (Dave_Darling @ Feb 9 2006, 09:44 PM)

As I said before, the optimum shift point is past the peak power rating by enough that the power in the new gear's RPM is the same as the power in the old gear's RPM.

For the power to be the same in the next gear is assuming the you have a perfectly flat power curve.

However, with most stock engine/transmission combinations, shifting at peak HP will generally have the engine drop to peak torque ready for the next gear and the accleration continues.

QUOTE (Dave_Darling @ Feb 9 2006, 09:44 PM)

Due to the way the gears are spaced, you want to shift a little higher in the lower gears and a little lower in the higher gears. But all of your shifting should be done somewhere between 5000 RPM and redine.

I agree that shifting at redline (or above) in the lower gears is going to give the best accleration and short shifting in the higher gears (by upto 500rpm G50 example, the only gear charts I have plotted).

Using the gear ratios of a G50, the RPM drop from changing from 2nd to 3rd is 2200 rpm. Using your theory the engine is making the same HP at 6800 rpm as it is at 4600 rpm. If we have a look at Bill's dyno the HP drop from 6500 to 4500 rpm is 74hp but the torque goes up by 15.

Peak torque is the starting point for all race teams to determine gear ratios and shifting points. After this, minor adjustments are made to suite track conditions.

Bill,

I've got a Fabspeed chip in my '95, and the PO thought it added about 10% to the curve. Since the stock chip is sitting in a drawer somewhere I couldn't tell you the difference.

If its easily "borrowed" you can take it and test it if it helps.

Rob

I believe you can pull about 320 out of a bone-stock 964 block. That's what we're getting out of my dad's 1992 964 and as far as we know, he's only got the primary muffler replaced with a straight-pipe, PO might have chipped it.

Hi Michel,

Thanks for the lunch offer...next time I'm in town (I will be!) we need to get together. I'm now in Toronto and will leave for Philly tomorrow (Saturday)....on to Allentown and then Horsham and then San Francisco before returning home on Friday, Feb 17th.....

Whew...gotta keep working to pay off that 914 debt!

Bill P.

Partrick, I answered some questions on the 901 behind a 3.6 on your other thread, but the G50 really shifts nice compared to the 901 or 915.

Unfortunately, I never got a chance to try my 915 WEVO box, but maybe Andy S (Wyld6) will chime in about the characteristics.

As far as shift points I'll play around with them but I plan on shifting before redline when possible to extend engine life....

Bill P.

Hi Rob,

Thanks for the offer on the Fabspeed chip! I may just have to take you up on it. I probably will try to figure out how to chassis dyno the different chips I may go for and then settle on one. This isn't that easy as I'll have to have someone swap the chips for me in the ECU.

Thanks,

Bill P.

Fun stuff!

When's your next track day, Bill?

I'm going for March10th/31st at Thill with Trackmasters.
Both are Fridays.


KT

QUOTE (Sideways @ Feb 9 2006, 09:15 PM)

For the power to be the same in the next gear is assuming the you have a perfectly flat power curve.

Umm, nope! Picture a bell curve. The power goes up to the maximum, then comes back down again. Theoretically, you want to shift when the power on the "comes back down again" side is equal to the power in the new gear on the "going upward" side of the curve.

QUOTE

However, with most stock engine/transmission combinations, shifting at peak HP will generally have the engine drop to peak torque ready for the next gear and the accleration continues.

Now you're the one who is assuming a particular torque curve. Check the stock four-cylinder curve some time. Peak power is at 4900 RPM, peak torque is at 3500 RPM. Shifting at ~5500 will never, that I can recall, drop you 2000 RPM to the peak torque.

QUOTE

Using the gear ratios of a G50, the RPM drop from changing from 2nd to 3rd is 2200 rpm.  Using your theory the engine is making the same HP at 6800 rpm as it is at 4600 rpm.  If we have a look at Bill's dyno the HP drop from 6500 to 4500 rpm is 74hp but the torque goes up by 15.

I think you have totally misunderstood me. (Oh, and where is that RPM drop quoted? Probably not if you're shifting from 2nd to 3rd gear at 2200 RPM in 2nd, huh? Perhaps at 6000 RPM? Or somewhere else?) I never said that the engine will make the same power at any two given RPMs. I was saying that there exists some road speed where the power made by the engine in the lower gear is equal to the power in the higher gear. And that is the road speed where you want to change gears.

QUOTE

Peak torque is the starting point for all race teams to determine gear ratios and shifting points.  After this, minor adjustments are made to suite track conditions.

Not true. The peak torque number (and the peak torque RPM for that matter) is almost completely irrelevant. The starting point for determining gear ratios is either the power curve (the whole graph, not just a peak number!!), or is a list of what the terminal speeds on the straights on a given track are expected to be.

--DD

Here is a graph of the data of the dyno pull seen at the start of this thread. From the graph, if one looses ~1000 RPM's when shifting btwn 3rd to 4th to 5th, then the 'best shifting would occur at 6000 RPM's???

I found some gear ratios for a 915 box. These are not stock ratio, but for a reference they are OK. To better understand 'where to shift', a graph of the 'effective' wheel torque has been calculated based on the gear ratio. Asuuming the math is correct, here a graph of the 'wheel torque vs gear ratio' based on the earlier dyno chart.

Here is a listing of the stock ration 915 7:31 R&P Box and a torque chart.

I have a line on 3.6s from Germany......can get them to LAX customs house and the more pre-ordered the lower the shipping costs.

964s, 993s with or w/o variorams.....

QUOTE (Racing914six @ Feb 11 2006, 06:58 AM)

To better understand 'where to shift', a graph of the 'effective' wheel torque has been calculated based on the gear ratio. Asuuming the math is correct, here a graph of the 'wheel torque vs gear ratio' based on the earlier dyno chart.

If you really want to see how it works, re-do the lower plot so that your horizontal axis is road speed. That is, multiply the RPMs by the gear ratio and the R&P ratio and divide by the OD of the tires. That will give you a graph of thrust vs. speed. Do that for each gear, and you will see where the shift points are pretty easily--they're where the graphs cross!

BTW, if you assume that you lose 1000 RPMs when shifting near the max RPM of the graph, then according to the HP graph you should shift at the max RPM. Or a bit beyond if you're willing to run up past where the dyno test went.

--DD

....or you can wind it up till the limiter pops, then stuff it in the next gear

I'm taking different tack this year. Speed in gears. Swaping out gears in even a 901 can be a bit pricy. Theory is lovely, but what speed (or rpms) to you need to effectivly negotiate a given section of track? Big buck race teams use this to set up gearing. Low buck clods like me have one trans and do the best we can with that.

Yep...If you are like me, you do best when it's an all second gear course.

The top end at 7k rpm's in 2nd gear is 56 mph. That's 12 mph faster than a FOUR at 5500 rpm's. A clear advantage.

I'm ready...


KT

QUOTE (trekkor @ Feb 11 2006, 11:09 AM)

Yep...If you are like me, you do best when it's an all second gear course. The top end at 7k rpm's in 2nd gear is 56 mph. That's 12 mph faster than a FOUR at 5500 rpm's. A clear advantage. I'm ready... KT

Aye, 2nd gear rules but 56 (58 in my case) tain't fast enuff.
If I jack the limiter up to 7300, I get close to 65 out of 2nd which ought to keep me off the "bong-bong" on most courses.
38 in 1st will be up to 43+. In the past, I've driven 1st gear courses. The back end steers the car....what a hoot
Many of our courses have starts that I needed to short shift out of first. Shouldn't have to now.

This was somethin' I learned from the Boxster guys who often drove the whole of our courses in 1st gear. Hard core AXers.

QUOTE

I get close to 65 out of 2nd

I want an "H" 2nd gear, too.

In fact, give me a "D" 1st while you're at it.

"D-H-M-S-X"

Bring $$$


KT

I'm using B 1st & GA 2nd.
The C 1st is easier to find, but not so gud for accelleration from a stop. H & a 904 mainshaft was just too damn expensive.
I got 2 GAs with gears for about half that price.....yes, I fear for the health of the mainshafts with the abuse I'll be giving them.

DD,

With regards to multiplying by R&P and then divide by tire's OD, the chart's slopes remain the same because only a constant is being used (linear relationship). The values change, but the slopes are the same. Besides, if one was to uses this data to calculate road speed, should not one use the tire's circumferance C=D*(pi)

The slopes do change, because the graphs get stretched out horizontally, by different amounts per each gear. That changes where the graphs intersect, if indeed they do within the region we have info for.

You are correct about using the circumference of the tire, not the diameter. However, the circumference is proportional to the diameter, so that merely stretches all the graphs by the same amount. It'll throw off the actual speeds, but it will still illustrate how the graphs cross.

I wish I were better with Excel, or I could come up with thrust/speed graphs like I've seen elsewhere. A 944 guy graphed his out and posted them on his Rennlist member site, but I don't remember which one any more.

--DD