To preface, I am well aware my 83’ US spec 944 is no Lamborghini and I don’t expect any jaw dropping 0-60 times or anything of that nature.

Recently I’ve been attempting a 0-60 time on a level private road with no bumps or any other interference to my speed, and the best I can muster is a measly 12 flat, Im aware the 944 factory was supposed to be in the 7-8 range and my shifts aren’t exactly perfect but this is shifting at 5.5k and wide open. Knowingly I would expect sub 10 hopefully considering I only have 95k on the odo, but I’m still far off.

I am not sure what tests to run besides vacuum to see why I am getting such poor acceleration or what to check/ repair. I have already checked my vacuum system and there is seemingly no leaks.

Any advice as to what to do to possibly bring my 944 back to 80’s Porsche speeds rather than 80’s civic would be greatly appreciated.

( side note with the details, 0-60 was achieved in 3 gears,
1st shifted at roughly 4-5k rpm and 30 mph
2nd shifted at roughly 4-5k rpm and 42 mph
3rd went from 42-60 at roughly 4k rpm

I have installed a short shifting kit. As well as a trans linkage and a throttle cam, all which improved time and response.

Sparks are new, however besides that no knowledge on the age or strength of any vacuum components or the fuel pressure systems. )

thank you.

 

you are upshifting way too early.

Retest, but run it to redline (6500) before shifting.
in an NA 1st gear goes to 35 mph, 2nd goes to 58. only when you are almost to 60 do you need 3rd.
if you are upshifting from 2nd at 42mph you have given up 25% of that gear's rev range! where its acceleration is significantly better than 3rd.

6500 is not going to hurt anything.

 

Like V2Rocket states, use the power of the top of the rpm band. Short shifting saves money, but costs time. The engine should rev to redline easily, with no harm to the engine.

Remove all unnecessary weight from the car. Remove the passenger. Lose some weight.

Do a compression check. USA spec cars are 9.5 to one, ROW cars are 10.6 to one... Consider rebuilding the engine with high compression pistons.

 

You could take a video of a 3rd gear pull to redline at full throttle and we can compare that to the published acceleration plots. 0-60 is tough to do, driving skill and track surface, etc. affect it considerably.
Video the tach and speedo, and check your speedo with a GPS app or similar.

-Joel.

 

Where does the torque band start and stop on a 8 valve NA engine? Does it go all the way up to 6500?

 

ok, I will do a run where I’ll redline fully, I figured redlining (or in the 944’s case yellow lining lol ) would be harmful for a 40 year old engine, but considering I’ve kept carful care of it, nothing should happen theoretically,

I will repost with updated times.

I however would guess this will only shave a second or maybe 2 if I’m lucky and fast off this time, which still leaves a solid 3-4 seconds before reaching factory time

 

Looks like Porsche ran it up to about 35 MPH in first, then ran all the way to 60 in second.

 

Manifold pressure is important, fuel pressure and delivery volume is important. Tests on each of those systems will provide some good data.
Compression and subsequent leakdown testing will also be valuable in assessing the ring and valve sealing.
Are the tires original diameter?

 

FYI

 

i did another launch going to 6500, Basicly same result. A little quicker by maybe 1/2 of a second but it really falls off on higher rpm

 

What do the spark plugs look like?

 

My dyno from 10+ years ago. Fully stock early 2.5 engine.

 

Thanks for the chart, V2! Great to know! I bet that your V-6 does a lot better!

 

Looks like Porsche nailed the 2-3 shift for shifting at redline for maximum acceleration. Maybe, with this particular engine, shifting 50 to 100 RPM early would help, but not by much. The engineers have to pick realizable gear ratios and this is likely the best possible configuration for data averaged from several engines. 1-2 shift is obviously best at redline, and 3-4 looks like it would be best around 6300. Just my eyeballing, and only with this particular engine (on that day, at that temperature, at that atmospheric pressure, with that tank of fuel, etc., etc., ...)



Fun little investigation.

 

yes, the extra 100hp/ftlb helps a little!

i've timed mine in the low 5 seconds for 0-60.