Engine Build Dyno Results

[WolfeMacleod]

That does seem very low, to me.
My 1985 was on a dyno a month or two ago.

This engine had never been rebuilt, and has no mods.

At the wheels, according to the operator.

[JohnJL]

Wow, you look REALLY lean there. Did you do any adjustment?

[WolfeMacleod]

Originally posted by JohnJL
Wow, you look REALLY lean there. Did you do any adjustment?

Talking to me? If so..no adjustment...

[CruiseControl]

Wolfe, if you wish to keep the smile on your face, don't get these numbers checked at another dyno shop.
Paul

[WolfeMacleod]

Originally posted by CruiseControl
Wolfe, if you wish to keep the smile on your face, don't get these numbers checked at another dyno shop.
Paul

One of the books I have read suggests that this car came from the factory with 202hp.
The Porsche website says 231. I'm told they measure at the flywheel...adjust for transmission loss, and that's pretty close.

The car has 40,000 miles on it, so I would assume it's not very worn out. Compression and leakdown results were spectacular.
We'll run it again, and if the numbers are much different, I'll ask the first shop about it...

[CruiseControl]

Wolfe, I understand your dyno HP numbers are at the wheels, not flywheel. The 1985 with engine Type# 930/21 has 207HP flywheel according to Bruce Andersons performance handbook. A June 1986 drivers manual shipped with a type 930/21 engine states 217HP (flywheel). The 217HP according to BA handbook came with the type 930/25 in the 87-89 Carrera. (yet a further discrepency)
The 231HP was for ROW type# 930/20 engines.

So unless you have type# 930/20, or previous owner(s) has done engine mods, the numbers you have are unusual. This is based on the flywheel HP = US dyno rear wheel HP *1.15

If you have a 930/21 or 930/25 I suggest using a DIFFERENT dyno to confirm your numbers.

I agree with John on the A/F ratios. The wide band O2 sensors / calibration, can also be out of wack.
Find another shop to get ALL numbers cross checked
Paul

[ttweed]

Originally posted by CruiseControl
I was told many years ago that HP difference relative to temperature is about +1% per 10degF (5.55degC) fall in temp.
Maybe, some one else could comment and also relate to the changes relative to humidity.

Most dyno software will calculate these corrections automatically and include them in the output figure. I know the Dynojet 248C I tested on would do this to SAE specifications. Are the original HP figures shown for the Dyno Dynamics corrected or uncorrected?

The equation for the dyno correction factor given in SAE J1349 JUN90, converted to pressure in mb, is:


where: cf = the dyno correction factor
Pd = the pressure of the dry air, mb
Tc = ambient temperature, deg C

The pressure of the dry air Pd, is found by subtracting the vapor pressure Pv from the actual air pressure, since wet air is less dense than dry air. It is the relative density of the air charge which effects the engines ability to make power.

Humidty is less of a factor in air density than temperature and air pressure, but it is significant. In playing with this HP correction factor calculator developed by a fellow in Colorado, I substituted values to change relative humidty by 10%, from 24% to 34%, while keeping all else equal, and the relative HP changed by .4%. At 100% humdity, however, it changed by nearly 3%. In comparison, a 30F change in temp (from 60F to 90F) yields about the same 3% change.

TT

[jpnovak]

John, I was looking at your AFR curve. I notice that the average is 12.2 - 12.4:1 through the rpm band. Looks good and flat. I might suggest you try to shift the entire curve(tuning map) up so that you run at 12.8-13.1:1. This will be more in line with peak power for a NA engine.

Otherwise your tuning looks good. I drove my EFI conversion the other day for the first time. It ran so much better than I expected and was surprisingly easy to improve on.

[EarlySport]

Considering the compression ratio, induction, and intended use of the car, aren't they really small cams ? Surely a lot of power is being left on the table relative to a set of DR60 or DR80 cams ? Of course if area under the curve and keeping peak power to a lower level for your power-to-weight classification is most important this may not be the way to go..

Craig H

[JohnJL]

The cams were originally meant for a street car. I just has a new-to-me 71 Targa arrive today, I might switch this engine over to the street car, put those solex cams in and put its weber 40's in that...

[joetiii]

JohnJL,

I am in the midst of sorting out a top end rebuild for my stock US '82 3.0. And while the dyno you used may not have high numbers as compared to US dynos, (doesn't really matter a whole lot IMHO),

I'm liking the results.

You have 145 lbs of torque from 3200 RPM all the way to 6500. That is a killer torque curve for a street engine. From 5250 and above you have a nice horsepower peak up to 6400. I believe the shape of the curves is more important than the actual raw numbers.

My US 3.0 makes peak torque at 4600 RPM and peak HP at 5800 RPM. Stock SC cam with PMO 40s, SSIs and M&K muffler.
the car makes more torque than horsepower and I can feel that the engine runs out of breathe at 6 grand. My torque curve runs flat from 2700 to 5600. Nice around town, but theres no massive rush to redline.

I am curious whether you are using your stock 83 heads and had them machined for the second plug, or whether you chose the earlier 3.0 heads?

I am considering the larger intake heads and think they would work well with Camgrinders Mod S DC40 cam. Thats a bit more cam than you have, and I think you are at the max cam with Fuel injection. Correct? I'm not sure what your intake setup is.

In any case, the higher compression ratio improves the low end torque a bit and makes for a nice streetable engine. The last question I have is how does your butt dyno feel as compared to before the engine mods?

joe

[JohnJL]

Hi Joe,
I've been travelling, sorry for the late reply.

I used later 83SC heads, but smoothed out the ports to match the 3.2 intake manifold ports.