Can an engine be de-tuned easily?

[chopthebass]

Most here seem to want more power but I am wondering how easy it is to de-tune an engine for less power. I really think I may have over-egged my ommlette!

[David Hodgkins]

Can you give us a breakdown of the specifics of your motor? That would help determine what steps you might take; IE heads, cam, etc.

[chopthebass]

I will find out the details from my engine guy.

[chopthebass]

Some of this doesn't mean a lot to me, but here you go...

Probe 427 Pro Street short block
Edelbrock E205 heads
Edelbrock Victor intake
SDS EFi system
Comp Cams Xtreme Energy 5.0 roller, 232/240, 565/574
Comp cams hydraulic roller lifter retro kit
MSD distributor
Mallory Ignition box

[Bob Cowan]

That's a pretty mild engine, IMO. Should make good power and be very easy to drive on pump gas. If I were you, I'd just install and drive. Worry about it later. But I bet you won't want to de-tune it.

[chopthebass]

Bob do you mean mild as in low-ish horsepower? I have no idea what the HP will be. Just my engine guys estimate.

[Arvin]

I've got a 408 in mine pushing 525 hp - wish I had more!

[David Hodgkins]

Bob do you mean mild as in low-ish horsepower? I have no idea what the HP will be. Just my engine guys estimate.

What is his estimate? BTW do you know what pistons and rods you are using? Compression Ratio?

[mikeinatlanta]

You have a few options for detune. You can directly take out throttle with either a stop or an adjustable ratio linkage as I did. I can adjust mine such that full pedal travel delivers 1/8 throttle. If you go the throttle stop route, you can put a spring in the linkage between the cable and throttle body that will allow the pedal to have full travel without stressing the throttle stop or linkage.

Other ways to take power out would be a restrictor just downstream of the throttle body, quiet mufflers, or one of those mini air cleaners guys like to use on cobras.

[Jeff Kleiner]

Without trying to sound like a wise a$$ (my wife tells me that I don't even have to try, it comes naturally ) you need to remember that no matter how much power you have you do not have to use all of it---i.e.; train yourself. Iron Man Bob has already chimed in... many times he has said "There is no such thing as too much power, only a lack of control" or words to that effect. That said though an easy way to take the edge off and kill some power without making any mechanical changes is to simply back some timing out of it. After you drive it for a while and get comfortable you can tune it back in.

Jeff

[Duke]

Yes. Easiest way is to choke it with a restrictor plate or smaller carb.

[chopthebass]

What is his estimate? BTW do you know what pistons and rods you are using? Compression Ratio?

David I don't know the compression ratio. I will try to find out. His estimate is 550hp

[bobl]

Along the line of JK's thoughts. Having aftermarket EFI you most likely have the option of timing retard function. On mine, I connected a toggle switch that activates the programmable timing retard function. Basically giving it a street/track mode. You can really tame the engine down by pulling timing out of the curve.

[6t8dart]

That's not so mild, I would call it healthy street build, in my estimate, the cubic inches, heads, intake, cam...I guess 525 hp. Probably a good flat torque curve...would be great for a mustang. But it would not be one I (personally) would want in a daily driven 2200 Lb roadster. Light weight, short wheelbase, open air roadster...makes that fun for some people, a little too much for others. Don't get me wrong, I drive a 485 hp car as a daily driver, but it's modern, comfortable, and computer tamed.

If you want to de tune it, it's not hard, you will have to change two major components, cam and intake. Go with a performer RPM intake and a Comp 35-512-8 roller cam, this will retune and make it idle smoother, less lumpy, but it still will have a ton of torque. You will probably have to have the fuel injection system retuned, maybe a few small components, pushrods, gaskets, oil, etc. I think this would be a very fun engine too.

http://www.summitracing.com/parts/cc...view/make/ford
35-512-8 camshaft, Hydraulic Roller Tappet, Advertised Duration 258/264, Lift .480/.480, Ford, 5.0L

[CraigS]

If you really feel the need go w/ some type of partial throttle limiter or a restrictor plate under the carb. I can't see any reason to be buying new parts to replace new parts. I suspect that a year from now you will want to at least try removing your limiter/restrictor. BTW, if you haven't already go w/ a Russ Thompson gas pedal. Play w/ the linkage ratios to get an extra long, so very controllable, pedal travel.

[Erik W. Treves]

just take a few degrees of timing out of it, or drop the rev limiter...easy enough with EFI....have 2 files...Most of the efi systems out there have 2 modes or multiple file you can drop in there......or do a throttle stop.

[chopthebass]

Interesting that I might be able to have two EFi files. Its all hypothetical right now. I might drive it and love it!

[Bob Cowan]

Bob do you mean mild as in low-ish horsepower? I have no idea what the HP will be. Just my engine guys estimate.

Two big factors make an engine mild or wild: Compression, and camshaft design. You cam looks on the low end of "wild" for a stroker. That's a good thing, because it will make good low end torque, be fun to drive, and drive very smoothly. Compression should not be so high that it needs race fuel all the time. With that cam and your altitude, you static compression should probably be around 10-10.5. Again, good power, easy to live with.

Try to keep dynamic compression around 8.0'ish. Certainly no more than 8.5 - and That's pushing it.

David I don't know the compression ratio. I will try to find out. His estimate is 550hp

With that cam, you would need a lot of compression and some really good heads to hit those power levels. If you use a program called "Desktop Dyno", you can get a fairly accurate idie of what your power levels will be.

Interesting that I might be able to have two EFi files. Its all hypothetical right now. I might drive it and love it!

Depends on the EFI system you're using. My EFI system is capable of that with the flip of a switch under the dash. But most ECU's are not that capable. You'll have to load a new file from your laptop every time you want to change it.

[CraigS]

You could retard the timing but probably be limited to maybe 5-7 degrees. I am guessing there but I know that retarded timing leads to overheating so there is definitely a limit.

[Raceral]

Nascar is running a little over 400hp on restrictor plate races and running 198... for what ever that's worth. Makes me shake my head when I hear folks saying 500 is not enough... and they don't even race.