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making car produce less power - i know strange question, but..

General engine tech -- Drag Racing to Circle Track

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Walter R. Malik
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Re: making car produce less power - i know strange question, but..

Post by Walter R. Malik » Wed Jul 29, 2020 10:05 am

I would simply restrict the exhaust side somehow...
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Re: making car produce less power - i know strange question, but..

Post by dannobee » Wed Jul 29, 2020 10:15 am

79 vette had a bead/pellet type catalytic converter on it in factory trim. Back in the day, we had a LOT of problems with those plugging up, to the point where they sometimes wouldn't even start. Replacing the converter fixed all of that and had no noticeable effects, i.e., no burned carpet, fried underhood components, etc, so an exhaust restriction/exhaust throttle would work with no ill effects.

If it still has full length exhaust, is there any way to install a catalytic converter "test pipe" with a significantly smaller opening? The restriction would have to be smaller than 1" cross section in order to reduce the power down to where you need.

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Re: making car produce less power - i know strange question, but..

Post by Bruce68 » Wed Jul 29, 2020 10:18 am

Does your EFI system allow you to disable cylinders?

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Re: making car produce less power - i know strange question, but..

Post by ustahava67 » Wed Jul 29, 2020 10:27 am

if you have a captured lifter remove 4 intake rockers ;)
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Re: making car produce less power - i know strange question, but..

Post by Belgian1979 » Wed Jul 29, 2020 11:05 am

anyone with pipemax (my licence was lost with one of my older laptops) that is willing to put in some number, please give me a pm.

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Re: making car produce less power - i know strange question, but..

Post by californiamilleghia » Wed Jul 29, 2020 11:39 am

I assume they will have the engine number , so swapping an engine for the test will not work ,

And when it will only do 2500-3500 RPM the Tester will know something is up , and the Testing station is owned by the government ,

How far do you want to take it apart ? Lowering the compression , stock 70s USA Smog cam and restricted exhaust will work ,

Are there Private shops that can do the basic test so you know it will pass ?

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Re: making car produce less power - i know strange question, but..

Post by chimpvalet » Wed Jul 29, 2020 12:10 pm

I think Tuomo's method is the most sound, given that the I/C engine is foremost an air pump. Choke the intake airflow and power is reduced without collateral issues such as the heat added when timing is retarded. Throttle stop is just so easily accomplished compared to all else, happily also the easiest and quickest to disable when taking at run at Spa! Collapsed catalyst or otherwise bunged up exhaust is another way to choke off power, less easy to conceal I'd say.
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Re: making car produce less power - i know strange question, but..

Post by Belgian1979 » Wed Jul 29, 2020 12:49 pm

No engine number is not of importance. I mean how many cars have had their engines swapped. Rule is same number of cyls, same fuel, same delivery of fuel, same power and same total displaced volume.

As for throttle stops, that will essentially be just as much noticable by anyone as a revlimit.

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Re: making car produce less power - i know strange question, but..

Post by ptuomov » Wed Jul 29, 2020 1:10 pm

Belgian1979 wrote:
Wed Jul 29, 2020 12:49 pm
As for throttle stops, that will essentially be just as much noticable by anyone as a revlimit.
No.
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Re: making car produce less power - i know strange question, but..

Post by chimpvalet » Wed Jul 29, 2020 1:12 pm

Throttle stop must be supplemented with an alternative pedal or throttle lever ratio so as to conceal the reduced intake. Not hard to accomplish.

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Re: making car produce less power - i know strange question, but..

Post by David Redszus » Wed Jul 29, 2020 1:16 pm

ptuomov wrote:
Wed Jul 29, 2020 1:10 pm
Belgian1979 wrote:
Wed Jul 29, 2020 12:49 pm
As for throttle stops, that will essentially be just as much noticable by anyone as a revlimit.
No.
Agreed. A throttle stop is the easiest and most adjustable method to reduce air flow and power. It will not produce a hard rev limit.

Another solution is to use dummy air filters that restrict air flow.

Either method can be tested by driving the car uphill.

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Re: making car produce less power - i know strange question, but..

Post by ptuomov » Wed Jul 29, 2020 1:26 pm

David Redszus wrote:
Wed Jul 29, 2020 1:16 pm
ptuomov wrote:
Wed Jul 29, 2020 1:10 pm
Belgian1979 wrote:
Wed Jul 29, 2020 12:49 pm
As for throttle stops, that will essentially be just as much noticable by anyone as a revlimit.
No.
Agreed. A throttle stop is the easiest and most adjustable method to reduce air flow and power. It will not produce a hard rev limit.

Another solution is to use dummy air filters that restrict air flow.

Either method can be tested by driving the car uphill.
I would do both in case the technician get curious and finds one of the cheats.
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Re: making car produce less power - i know strange question, but..

Post by thedynoguy » Wed Jul 29, 2020 1:35 pm

so the throttle stop is too obvious. Surely there is a way to limit the throttle opening. Even if it's just lengthening the throttle cable so the throttle pedal only moves 1/2 of it's travel. Is the inspector really going to look under the air cleaner mechanism to see if it's going WOT? Just sayin'...

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Re: making car produce less power - i know strange question, but..

Post by Belgian1979 » Wed Jul 29, 2020 1:39 pm

A clarification : during regular controls they cannot disassemble anything on the car. I could potentially make plates that mount in my airbox on top of the stacks and reduce the opening to about half of the widest cross section. Go to a rolling road dyno, have it dyno tested and send them the sheet along with a report.

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Re: making car produce less power - i know strange question, but..

Post by ptuomov » Wed Jul 29, 2020 1:47 pm

Belgian1979 wrote:
Wed Jul 29, 2020 1:39 pm
A clarification : during regular controls they cannot disassemble anything on the car. I could potentially make plates that mount in my airbox on top of the stacks and reduce the opening to about half of the widest cross section. Go to a rolling road dyno, have it dyno tested and send them the sheet along with a report.

If you just put a restrictor orifice in the air filter but no throttle stop, you’ll have to retune your whole alpha-N fuel table.

If you use a throttle stop, any additional retuning you need to do is tuning that you should have done in the first place and should leave in after removing the throttle stop.

A very restrictive throttle stop and massive ignition retard on load rows indexed by larger than stopped throttle opening angle would be a good combo, as even if the throttle stop is removed it will be down on power.
Last edited by ptuomov on Wed Jul 29, 2020 1:57 pm, edited 1 time in total.
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