Peak Power and Torque

[1owner69Elan]

I must say also that whenever power and torque curves are posted on this site I very rarely see the data below about 3,000RPM. For a road engine 1,000 - 3,000RPM is an important speed range. It seems a lot of the engine builders don't like to disclose the data in that range!

There are some inherent limitations in measuring the lower rpm ranges. Not just an engine builder's "failure to disclose":

https://www.hotrod.com/articles/dyno-testing/

[2cams70]

There are some inherent limitations in measuring the lower rpm ranges. Not just an engine builder's "failure to disclose":

Sorry but that article is rubbish. I work for an OEM and engines are always dynoed as low as possible. Usually from around 900RPM. Large Diesel engine for example produce enormous torque at low RPM and there's no issues with measuring it.

[nmauduit]

There are some inherent limitations in measuring the lower rpm ranges. Not just an engine builder's "failure to disclose":

https://www.hotrod.com/articles/dyno-testing/

Due to the EU's Global Data Protection Regulation, our website is currently unavailable to visitors from most European countries.

apparently there are other limitations, too

[Europa88]

Yes I had that flag up too

[2cams70]

Yes I had that flag up too

You Europeans obviously have good taste if that article was blocked. Here it is as a PDF. It's rubbish. You can measure engine torque at lower RPM ranges and if it is likely to damage your engine running at WOT at low RPM then something is seriously wrong with how you have it set up. 2,000-3,000 RPM WOT is quite a reasonable operating range for a road car. An article that's been obviously sponsored by the engine tuning industry ! Don't believe everything you find on the internet!

[Europa88]

Thanks for the PDF

[1owner69Elan]

Hmmm.

I think we may talking about different things. Different types of engines, applications, and perhaps different types of Dynos.

1.

I work for an OEM and engines are always dynoed as low as possible. Usually from around 900RPM.

Sounds like you are perhaps talking about large diesel/maritime high torque/low rpm applications. Not aware of this dyno protocol for auto engines but ?

2.

if it is likely to damage your engine running at WOT at low RPM then something is seriously wrong with how you have it set up. 2,000-3,000 RPM WOT is quite a reasonable operating range for a road car

.
The typical engine dyno is directly coupled (effectively in 4th gear). I don't usually let my car drop to 2000 rpm in 4th gear and then go WOT. While the car might be able to marginally handle it, lugging it like that stresses the engine, including potential destructive knock.

3. My understanding is that there are a different Dynos offered depending on the application (torque ratings, rpm ranges, ..). Why would these exist if all Dynos could simply capture a broad rpm and torque range?

4. When my engine builder was dynoing my engine, I too was interested in the hp/torque at lower rpms. Using the Super Flow 901 engine (not chassis) water brake dyno, the engine/dyno just "bucked" at the lower rpms as if a car was in too high a gear. So, in the end, I have the dyno curve I posted earlier and can only extrapolate for lower rpms and/or use my "butt dyno" to sense performance. (We should remind ourselves, including me, that a dyno is best used in a relative sense, seeing the effect of tuning/modification changes not the absolute numbers. Bragging rights are nice but not really the best use.)

5. The engine builders that use or can afford engine Dynos are typically those looking at higher performance applications, including racing. They are looking for power and torque in the higher rpm ranges. They don't have the requirement to constantly start up a road car from rest.
As such, the Dynos that they use and calibrate are set up for the higher rpm ranges. I don't think you can accuse them of hiding information. They just don't particularly care about performance at lower rpms.

6. So I agree with you, as a general statement, that torque can be measured at lower rpms, but that is not the complete story. It does not appear to me that the cited article is utter rubbish and to be dismissed as tuning industry "propaganda".

But, on the other hand, I have a "grunty and unsophisticated" TC, so what do I know. At this point, I'll get my coat.

[Europa88]

I think your engine build. @ 1owner69Elan is pretty much the holy grail for a powerful road engine. Can I ask what cams you have and CR ratio if known?

[1owner69Elan]

I think your engine build. @ 1owner69Elan is pretty much the holy grail for a powerful road engine. Can I ask what cams you have and CR ratio if known?

Cams: From Kent Cams.
Lift .440" gross, .oo8" lash cold, 250 degrees duration measured at .050" lift. 105 lobe center on the intake and 107 lobe center on the exhaust, .010" lash on exhaust cam

Compression ratio: 10.25. Runs on pump gas (US 91 (R+M)/2 octane). The dyno results posted above are on lowly 91 octane California gas.

More information: viewtopic.php?f=39&t=35851&p=346040&hilit=+engine+dyno#p346040

The builder, Dave Vegher, of my engine got the cams from Tony Ingram (another world-class engine builder, Lotus7.com). I don't know if the cams are a catalog item or a proprietary Ingram profile. If you go to his website you can see some more dyno curves for a variety of rally/race engines of different displacements. I am sure Tony could help dial in a cam to fit your application.

Another master builder, John McCoy, also has short duration, high lift cams that others (e.g. Rohan - "rgh0") have had excellent results with as well. https://omnitech-engineering.com

[2cams70]

If you don’t want to go to the expense of a steel crank, rods, and forged pistons and are therefore restricted to an RPM limit of 7,000RPM stroking the engine will give you more torque at low RPM for any given cylinder head + cam spec. The gains at higher RPM will be less pronounced and the engine most certainly will be noticeably less smooth particularly if you spend a lot of time in top gear at highway speeds You will notice it sounding more busy and frantic at these speeds with the longer stroke. QED 420 cams in a moderately cleaned up cylinder head with sprint size valves and compression ratio will give you 145 - 150HP on top of a standard stroke bottom end.

[Europa88]

Thanks for the information guys!

@2cams70 QED 420 cams in a moderately cleaned up cylinder head with sprint size valves and compression ratio will give you 145 - 150HP on top of a standard stroke bottom end.[/quote]

Yes but that's essentially where I am now and the QED420 isn't much different to a Kent L14 cam and my question was go steel and free up some high RPM BHP or stroke for lower end tractability and a flatter torque curve. To be fair that's a decision only I can make based on what I want to do with the car. It will be primarily a road car with a couple or three track days a year.

I do prefer a high revving motor Tho....argh! It will come down to cost when I need to do a head refresh (tappet sleeves are virtually on their limit) I will take the lot out and do the bottom end as well.

Thanks again guys

[rgh0]

Thanks for the information guys!

@2cams70 QED 420 cams in a moderately cleaned up cylinder head with sprint size valves and compression ratio will give you 145 - 150HP on top of a standard stroke bottom end.

Yes but that's essentially where I am now and the QED420 isn't much different to a Kent L14 cam and my question was go steel and free up some high RPM BHP or stroke for lower end tractability and a flatter torque curve. To be fair that's a decision only I can make based on what I want to do with the car. It will be primarily a road car with a couple or three track days a year.

I do prefer a high revving motor Tho....argh! It will come down to cost when I need to do a head refresh (tappet sleeves are virtually on their limit) I will take the lot out and do the bottom end as well.

Thanks again guys[/quote]

Either approach of more capacity or more revs can take you to around 180hp. More capacity is cheaper than more revs and builds a more road usable engine. Both approaches need a cylinder head capable of breathing that well to work with a good high lift cam and the air flow a big capacity or high rev 1600 cc engine can try to develop. The advantage of a Europa ( or Seven) is that you have room for a better exhaust which is worth 5 to 10 hp compared to an Elan when your getting to the bleeding edge.

Of course the very very bleeding edge is both and around 210 hp possible with a big capacity high rev engine with the best head.

cheers
Rohan

[2cams70]

180HP - you are going to need a full steel bottom end for reliability regardless of whether the engine is stroked or not and you will loose some bottom end torque (I don't think the LTC is adaptable for VTEC - miracles don't happen here!) . QED claimed torque curve for the QED420 cam attached for reference. At least they have the decency to give figures down to 2,000RPM!!

I have to suggest also that unless you are racing it you need to carefully consider whether moving it up to the next level is really worthwhile. Your setpoint for what is good performance will rapidly move up a notch and it will no longer seem fast!!

[Europa88]

Rohan, this is an old picture of my engine bay and the exhaust system, which is a works type 47 copy with a repackable silencer.
lets say I put a stroked crank on my current engine what realistically could I expect? Could it make an extra 20 BHP?

[rgh0]

Rohan, this is an old picture of my engine bay and the exhaust system, which is a works type 47 copy with a repackable silencer.
lets say I put a stroked crank on my current engine what realistically could I expect? Could it make an extra 20 BHP?

With no other changes another 10hp is more realistic for a 100cc capacity increase. Your doing well at 147 hp now with your specification engine and 155 to 160 hp is what I would expect to be achievable with a 1700cc engine to that sort of specification also

With a well ported original head and big 1.625 / 1.4 valves and a 0.440 lift McCoy cam, and good exhaust you can get to around 170 hp from a 1700cc engine at 6500 rpm. I just helped a friend build one to this specification and result. This is consistent with the Vegher built 1700 cc engine dyno curve and engine specs shown earlier which achieved 181 hp at 6900 rpm with a new SAS head with bigger ports than you can get with an original head.

All these numbers are of course approximate as dynos vary and engine build details can make a significant difference also.

cheers
Rohan