914-6 finally gets it's dyno runs, The dyno raises more questions Options

[RogerPihlaja]

So, I finally found a chassis dyno that was willing to run my 1970 914-6. The 3.0 liter 911 SC engine had about 1000 break-in miles on it. The attached file has 3 hp & torque curves from 3 dyno pulls superimposed. A 6300 rpm redline was observed. As you can see, the engine is still pulling hard at 6300 rpm and would produce more power if it were spun faster. I have heard 3.0 liter 911 SC engines are safe to rev to 7000 rpm; but, I wanted to get confirmation before I tried it. The engine has a Clewett Engineering engine management system with MAP fuel injection, coil at plug electronic ignition, wide range oxygen sensor closed loop, 1-5/8" ID Billy Boat headers, and a twin outlet sport muffler. The valves, springs, pistons, connecting rods, and crankshaft are stock. There is a mild cam from WEBCAM (Grind #40) in it.

I was somewhat surprised at the shape of the torque vs rpm curve. The dip in the torque curve between about 2600 - 3600 rpm reminds me of the bad old days of emission controls with carburetors. The [Air]/[Fuel] ratio would often go lean just off idle resulting in a flat spot in engine response and driveability around town. Do I need to remap the fuel flow for more fuel in that rpm region? Or, what else might be causing this dip in torque? Also, the flat shape of the torque "curve" surprised me. Isn't there supposed to be more of a peak? This isn't some "tractor" engine?

By the way, the engine sounds great on the dyno! I have a video file with audio; but, it's ~31 mbytes. If someone has a way to deal with a big file on the website, please let me know and I'd be glad to share it.  TooSlo86_Racing_Dyno_Chart.pdf ( 599.22k ) Number of downloads: 96

[Cfletch]

You could always just post to youtube and drop the link in this thread!

[mb911]

160ish hp? That seems low

[brant]

Too bad they didn’t have an AFR on the chart
We use a dyno with AFR to know how to jet

[SirAndy]

160ish hp? That seems low

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Both the HP and torque seem low when compared to the stock 3.0L specs.
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[mepstein]

If you aren’t running a hot rod 3.0 to 7k, you are leaving a lot on the table.

Edit - Sounds like you need to find someone that can tune the FI/engine management system. The stock file is usually just to get the engine running and set a baseline. It's never going to run to it's potential with a stock tune. You mention a mild cam. Why? One big reason to use modern engine management is to tune for a non stock/hot rod cam. I'm not suggesting 906 style, no power under 6K but something that will make the engine come alive. With COP, one of the goals is managing higher than stock compression without having to go twin plug. So from what you described, I'm wondering what the goal was for this engine. Get rid of cis, get more power, make it look pretty, something else?

[RogerPihlaja]

Hi All,

Yes ~160 hp at the rear wheels is somewhat less than I had hoped for. That's why I started this thread.

I was hoping for about 200 bhp at the crank running on unleaded regular pump gas. Extrapolating the hp curves to 7000 rpm would pretty much get me to that goal, allowing for 10-15% loss from the crank to the rear wheels. Can the 3.0 liter 911 SC engine be safely revved to 7000 rpm? If not, what needs to be upgraded?

Can you suggest a dyno shop that has an [Air]/[Fuel] instrument on their dyno? Can you suggest someone to consult re tuning the Clewett Engineering engine management system?

Does anyone have any comments re why the torque curve is so flat and what is causing the low rpm dip?

[mb911]

Ok cam timing also confirmed correct? I have seen that many times

[targa72e]

Can you give us a little more detail on your engine and intake configuration. For reference having dynoed many stock or close to stock 3.0L I have an idea what to expect. A 3.0 L with big ports and 9.3 pistons with stock CIS and cams with headers and good muffler will put out 185HP +/- and 175 +/- torque at the wheels on a Dynojet. 9.8 pistons will get you a little more. If you ditch the CIS and go with better induction the torque stays about the same but you can get another 15-20HP on the top end. When I tracked my SC I shifted at 7K all the time, for years, Stock bottom end and springs.

john

[PlaysWithCars]

Sounds like you need to find someone that can tune the FI/engine management system. The stock file is usually just to get the engine running and set a baseline. It's never going to run to it's potential with a stock tune.

(IMG:style_emoticons/default/agree.gif) I'm suspicious that you have too rich AFR and too conservative ignition timing. I'd be looking real close at ignition timing curve as the biggest culprit. Even if the dyno doesn't have AFR capability, you should be able to monitor and log most of this through your engine management system(s).

[flyer86d]

It looks like you are leaving a bunch of power on the table. As everyone said before, recheck the cam timing and ignition timing. It should be stronger. My old short stroke 3.2 with GE-80 cams made 320hp at 7500 rpm. We shifted it at 7500 and would take it to 8200 in a short burst if we had to get by someone. Stock rods…. Sue once mistakenly got 3rd gear instead of 5th on the back straight at Watkins Glen shifting out of 4th at 7000 rpm. Don’t know what it revved to but it wasn’t hurt and we did a lot of track events after that….. SC’s are very stout! Perhaps the best that Porsche produced.

Charlie

[jd74914]

Interested in more details as well. Did you just put the Clewit kit on and hit a dyno with it's base map? This looks like the results of a super conservative base tune, ie: the kind provided by the manufacturer to get your car to start and drive on the road or to a dyno. Usually these have very conservative ignition timing and are quite rich. The expectation from the manufacturer is that you're going to tune it, though Clewit doesn't make that too clear on their website.

Is this the kit you're using?
https://www.clewett.com/index.php?main_page...products_id=491

It has the O2 sensor shown, was this installed? With an Elite ECU you have the ability to data log so you can record what's actually going in.

Note: You don't really need a 911 guy to tune, most competent tuners familiar with Haltech software/peculiarities would be fine. With data logging you might even have good luck with driving around and a remote tuner analyzing the data and sending you updated files.

[VaccaRabite]

A stock 3.0 only made 180HP at the crank.
I don't know the specs on yours, but if you are making 160 at the wheels, that may be an indication of a healthy stock rebuild. Assuming 15% drive train losses, your 160hp would be 184 at the crank, which is on the nose for a stock build.

It does look like there is better tuning to be done.

If its hot rodded - there is clearly tuning to be done. But not knowing the build, its putting out RWHP in line with a stock build.

I'd be interested in seeing your fuel and spark maps.

Zach

[Root_Werks]

A stock 3.0 only made 180HP at the crank.
I don't know the specs on yours, but if you are making 160 at the wheels, that may be an indication of a healthy stock rebuild. Assuming 15% drive train losses, your 160hp would be 184 at the crank, which is on the nose for a stock build.

It does look like there is better tuning to be done.

If its hot rodded - there is clearly tuning to be done. But not knowing the build, its putting out RWHP in line with a stock build.

I'd be interested in seeing your fuel and spark maps.

Zach

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Was thinking the same.

[Chris914n6]

Looks like they use a Haltech 750 ECU. You just need to find a Porsche tuner that knows Haltech.