Roush dyno test

[Laurent Gauthier]

Hello,

I just got the numbers from Roush on my new engine (to go into a SPF GT40 Mk1). It's a 351W - 427IR. All alloy.

RPM Tque HP
3000 441 252
3500 485 323
4000 462 352
4500 527 451
5000 527 502
5500 514 538
6000 478 547


Given the dip in torque around 3800 rpm, there seems to be a huge increase in power between 4 and 4.5k rpm: 350 to 450hp. I guess I'll need a light foot.

 

[Doug S.]

Good choice on the alloy block. Every pound saved is just that much less HP required to make the thing go fast.

Stroker Windsors usually have a pretty flat, smooth torque curve. Yours has a lot of variation.

Hold on when that tach hits 4K--it ought to be one, sweet ride!!

Doug

 

[Laurent Gauthier]

According to Roush, the non linear torque curve is normal in the case of injected engines - as is the case with mine.

 

[Paul Thompson 'Hooligan']

Hi Laurent -

Looks like you are going to have a blast with that motor....rockonsmile

Do you have any pictures of this engine / setup?? -

I'm expecting a similar dry-sumped unit to arrive in about 5 weeks time for installation into a GTD.. I presume you are using a ZF?

 

[Frank Catt]

I will be testing the same spec engine in an SPF Mk2 very shortly, after adding some better fuel delivery flow, and I will give my impressions then.

 

[Paul Thompson 'Hooligan']

after adding some better fuel delivery flow

Hi Frank -

Was this the car I viewed at your workshop last time I was there? - were the issues with Roush supplied parts? - or as originally fitted to the SPF?

I guess if you were converting the SPF from carb to inj then there would have been additional requirements for the fuel in the form of swirl pot(s) / lifter pump(s) etc etc...

Driving impressions should be interesting... keep us posted..

 

[Laurent Gauthier]

I was wondering if anyone knew why the torque curve on this engine could be going up and down like that. I'd like to understand why it is the case, but I have no idea where to look. In some older books I had on Ford small blocks, the charts there did not show a substantial difference in torque or power curves between injected / non-injected.
Suggestions and ideas are very welcome!
Laurent

 

[Chas]

Laurent,
Here isthesheet of our 427 aluminum engine which I posted yesterday on the Manufacturers Forum.
The explaination for your slight dip is possibly a function of the relationship between the chosen cam lobe design, the intake port and the header used. In short, a small reversion at that time in the RPM band.
We also sometimes see that in our A/F sensor readings where the mixture goes slightly rich or lean in that timeframe. Tuning your IR system's A/F ratio may improve that "hole".
You can see we experienced a very small richening of A/F between 5100 and 5400 RPM which caused a very minor torque dip. Overall though, for a carburetor, this one is well dialed in.

Good luck in your efforts.
Sorry for the poor quality image.

 

[Paul Thompson 'Hooligan']

Hi Laurent...

Interesting figures, there's a definate dip at about 3K and I can only see difference being caused by changes to fuelling / timing requirements. I wonder if Roush map for each individual motor built, or have a 'generic' map on file that they install for each build type??

I am expecting a similar spec all alloy 427IR in a dry-sumped configuration from them shortly, so it will be interesting to compare the figures they provide with that too.

When we dyno'd Roy's 347 Alloy Clevor - we had a dip at about 4K, that I managed to pretty much dial out by adjusting the fuelling in that range. I presumed it was a function of the runner capacity/flow characteristics that seemed to improve the airflow at that rpm. If I recall correctly, we added additional fuel as it was a tad lean either side.

I'm not sure whether the Roush provided map is 'locked' either, hopefully not, although I suspect it will be for 'warranty purposes'... Talking of which, what is your intended use for the motor and what warranty terms do you have??

Your dyno results plotted in Excel.

 

[Paul Thompson 'Hooligan']

Forgot to add - I took a ride with Frank in the Roush SPF MkII and very nice it was too. It is in fact a 402IR based on a steel 351, but still made all the right sounds although was not quite as 'thumpy' as I had anticipated. A friend has a 427 steel version and that definately sounds stronger, although it does not have a cross-over exhaust and is fuelled by a great big Holley... possibly why it seems 'thumpier' - (technical term )

I expect the fuelling for the SPF was tweeked to comply with emissions regs and is possibly not currently optimised for performance, no doubt Frank will give a full report at some point.

 

[Laurent Gauthier]

Thanks a lot for these replies. I understand better what is going on. Manowar, these are very nice engines you put together, I remember reading an article - I think maybe in Kitcar magazine. I see the slight dip you have in torque around 5k rpm, it is really minor.
I have posted the dyno sheet, and put it in Excel as well. P Thompson, sorry you ended up typing it in, I had this spreadsheet already but had not figured out how I could attach documents!
In any case I will definitely ask Roush if they can smooth out the curve a bit.

To answer some of the questions:
- I do not know to what degree the mapping is locked by Roush
- Intended use will be roads, maybe some track not too often
- As for the warranty, it's 2 years 25k miles if I remember correctly. Since I'd not want to lose it, I'll ask Roush to tune the engine

(Roush still has the engine, because I don't have my ZF yet)

Actually a side note on the ZF - ordered it before I ordered my car, still dont have it