Reducing HP, by adding head gaskets

[LMRacerWC]

Hi, we have a Lawn Mower racing series, where we are limited on HP output through our rules.
We use a standard Predator knock off 212cc engine, which pushes about 12+HP, with Govenor removed.
To bring them all into spec, we add head gaskets, to reduce the power.
My question is, if you have an out of box motor running say 13HP and bring it into spec (10.5HP), would it perform any different from an out of box motor of about 11.6HP, reduced to same 10.5HP?
Would the higher spec motor - prior to detuning - perform better at say low revs, etc?
TIA

 

[Rat]

Yes.
You are not really detuning as much as you are lowering the compression ratio, which lowers the engines efficiency (makes it work harder to burn less gas and waste more)

It's extremely counter intuitive to remove the governor and the go making the engine run poorly... leave the governor in at that rate and just lower its rpm

 

[bob58o]

What?

This whole concept seems nuts.
How does one do tech inspection to verify the output of a randomly modified engine of sizes and random modifications.

Why do you think a standard ungoverened makes 12+ HP?
How would you verify that a modified 13 HP engine makes 10.5 HP?

Do you have a dyno to test every engine?
If an engine is detuned for tech, why would it stay that way?

“My 350 cu in small block makes ten HP, I promise. Cross my heart.”

“How?”

 

[Rat]

What?

This whole concept seems nuts.
How does one do tech inspection to verify the output of a randomly modified engine of sizes and random modifications.

Why do you think a standard ungoverened makes 12+ HP?
How would you verify that a modified 13 HP engine makes 10.5 HP?

Do you have a dyno to test every engine?
If an engine is detuned for tech, why would it stay that way?

My 350 cu in small block makes ten HP, I promise. Cross my heart.

What I'm stuck on is this "detuning" is mostly just making the engine run like garbage... of course that costs power. But like seriously? There have been lawsuits over undelivered HP claims made by manufacturers

 

[bob58o]

Run What You Brung, or walk. It’s not my place to tell one how to moves their feet’s.

Stockcar racing where everyone runs a different displacement engine. Hmmm. 454cubic inches in a world of 358’s because… trust.

 

[bob58o]

I think I understand what’s going on.
We are running these on used vegetable oil. The estimated 50 octane rating requires less compression.

 

[Master Hack]

We use a standard Predator knock off 212cc engine, which pushes about 12+HP, with Govenor removed.

if you have an out of box motor running say 13HP

Wateaminnit! What am I missing here? Out of the box 212 running 13 hp? aren't the 6.5 "out of the box" Removing the govenor doubles the out put? So a 13 HP 390 would be 26 without the govenor, then? Wow, I'll be back in a few minutes...

 

[bob58o]

From what I can see here…

Somebody is trying to justify running a gx390 in a gx200 class by claiming the stock gx200 makes 12 HP and this “modified” 390 makes 10.5 HP.

If you ain’t trying to cheat, what’s the point in racing. But this seems obviously wrong.

Not sure who is going to buy this claim, but I’ve got a white glove / ketchup popsicle deal going on. Today only.

 

[Denny]

Why not just run a restrictor plate or a smaller carb. Lowering the cr will lessen the hp but how much is anyone’s guess.

 

[Darren]

I was going to type the exact same thing, restrict airflow through the carb, the governor just controls the maximum revs by overriding the maximum opening of the carb, First time I've heard of a GX governor halving the bhp of an engine.

 

[Rat]

I was going to type the exact same thing, restrict airflow through the carb, the governor just controls the maximum revs by overriding the maximum opening of the carb, First time I've heard of a GX governor halving the bhp of an engine.

Supposedly there is no governor anymore... if you actually read.

Either way it's idiotic... you want less power get a smaller engine. Simple as that

 

[LMRacerWC]

WOW!! What a lot of negative comments on a straight forward question!
The lawnmower series was derived from our sons running these little clones (Hoffmann 212cc HY7) on Mini Go karts. Their series has a strict scrutineering process and yes, the engines are run on a Dyno (see attached), to get them all within spec and sealed. On these go karts, they get up to 55MPH on track, running a 21T front Sprocket & a 71T rear sprocket
The organizers decided that the speed is a little high for these 7-10 year olds, on a Kart track and proposed to try different ways of reducing the power but still keep it within the budget series. So currently the engines run a 17mm Carb intake restrictor, as well as Head Gaskets, to get them in spec. As a matter of interest, these karts lap at the same times as the Tillotson T4 Mini 196cc. Karts.
This series has been running for over 5 years, as a budget, entry level racing series, using OTK/ Praga/etc. Chassis.
some of these engines have been running for well over a year, doing 12 race weekends a year, of 3 session of 15minutes per raceday, excluding practise days. So very reliable and competitive!

 

[Rat]

WOW!! What a lot of negative comments on a straight forward question!

What you call negative is simply realistic. You have found yourself amidst those who have many years (or decades) experience building and tuning these types of engines whether it is to race on a track, tear through trees, or putter around the farm is all irrelevant. This is a collective of invaluable information, however I for one am not idiot friendly and just don't play well with others in general.

The lawnmower series was derived from our sons running these little clones (Hoffmann 212cc HY7) on Mini Go karts. Their series has a strict scrutineering process and yes, the engines are run on a Dyno (see attached), to get them all within spec and sealed. On these go karts, they get up to 55MPH on track, running a 21T front Sprocket & a 71T rear sprocket. The organizers decided that the speed is a little high for these 7-10 year olds, on a Kart track and proposed to try different ways of reducing the power but still keep it within the budget series

Instead of some dumbass reverse engineering...

1. The inspectors need to be properly and adequately educated... it is painfully obvious they are not if they can't figure out the answer in 2 seconds or less.

2. That 21/71 = 3.38 final drive, so swapping gears is the INTELLIGENT and PROPER way to bring the speed down.

If you have the power coming out of these engines to move that 3.38 ratio with any amount of significant reliability (dyno may give you a peak output, but it doesn't count for real world physics such as drag coefficient and rolling resistance)
a 5:1 or 6:1 would smoke the current ratio off the line, accelerate like a bat out of hell out off apex, top out in the 30-40 range, and just be a whole lot more fun in general.

The fact they couldn't come the conclusion on their own that the best method of reaching their goal is not removing the governors, limiting the RPM to 3400-3600, and chainging the gear ratio is actually quite pathetic really.

Am I an A$shole, yep! Indubitably so!

You can trust I will always tell it exactly like it really is, and I don't care if reality hurts your feelings; not one damn little bit!

If my opinions or for that matter anyone elses offend you, that's completely your problem not ours.

 

[Denny]

Not being mean. We’re just honest straight shooters here. The only way the sanctioning body is to supply all the same sealed engines to everyone. They all must be built and dyno the same numbers. Or institute a claimer rule where anyone can claim the winners engine and the first 3 places engines for say $25.00 and your engine. They can not reclaim their engine from that person for the rest of the year and they after passing tech have to remove their engine in front of you and a track official. The low money keeps people from spending big bucks on their engines and engine programs. Everyone will know everyone’s speed secrets then. Keeps costs down too. Common in lower class stock car racing in the states.

The sealed engines is a tougher road to go people will still try to cheat with reproduction seals.

 

[Master Hack]

Those pics don't mean much. I can put up a dyno card for a LS7 and claim its a GX390!

 

[LMRacerWC]

Those pics don't mean much. I can put up a dyno card for a LS7 and claim its a GX390!

Agreed, i am not bragging about the output. The values are irrelevant.
My question is, if you have an out of box motor running say 13HP and bring it into spec (10.5HP), would it perform any different from an out of box motor of about 11.6HP, reduced to same 10.5HP,
Would the higher spec motor - prior to detuning - perform better at say low revs, etc?

whilst i also don’t agree with the procedure used (adding head gaskets)
I wanted to know if there would be any differnce between the 2 motors.

Whilst i hear all the comments, re the amount of power it produces, all the competitors’ motors are dyno tested on the same dyno and sealed with serialized seals, prior to being handed back to the competitors, so no cheating can be done. The carbs are also sealed so not to be removed or rejetted.

The playing field is pretty much level.
I was just interested in the variances in performances like low end torque, accelleration, etc. between the 2 motors.
Herewith a link of the karters using this 212cc engine

 

[Denny]

Cool. An engine with a longer stroke is going to make more torque than an engine with a shorter one. An engine with a bigger bore will spin up quicker than an engine with a longer stroke. So due to physics no, 2 engines with the same displacement but differing bores or strokes will not make the same power. You can’t take 2 engines of differing size and tune or detune to make the same power. Horse power and torque numbers will never match.

 

[Master Hack]

Ya ain't racing if ya ain't cheatin

 

[bob58o]

I’m not sure if the mph on the dyno image is correct or just convenient so 4700 rpm = 47 mph?

If speed is correct and gear ratio is 3.38 : 1, that would mean around 12” tires (11.4” by math).

If they get up to 55mph, they turn up to 5500 rpm.

Peak TQ 3100 RPM / 31 mph
Peak HP 4700 RPM / 47 mph
Max 5500 RPM (with 3.38 :1 Ratio) / 55 mph.

Assuming 2000 RPM clutch engagement
20 mph clutch lock up speed. <- (I don’t know if most other people consider this, or if I describe it correctly). Either the tires or the clutch must be slipping until this speed. Assuming decent traction, the clutch is slipping, getting hot, asking for multiple replacements before asking for a gearing change.

Now swap the 21T for a 14T…
5.07 :1 gear ratio

2000 RPM clutch engagement at 13.4 mph.
Peak TQ at 21 mph
Peak HP at 31.5 mph
43.5 mph at 6500 rpm
Speed / rpm limited by rev limiting coil
Valve float might happen at 5500 rpm without valve spring upgrades. 5500 rpm would be 37 mph.

6500rpm Rev Limited Ignition Coil for Predator/Clone 212 Engines

www.eccarburetors.com

A 16T would max out at 50 mph at 6500 mph.

 

[bob58o]

The powerband as shown on the big big block is from 3000 rpm peak TQ to 3600 rpm peak HP.
Only 600 rpm range.

The power band as shown on the small block is from 3000 rpm peak TQ to 4700 rpm peak HP.
The rpm range from peak TQ to peak HP is 3X as wide.

im not sure what this means for racing, or what your track looks like but I like a wider range… I think. At least with a single gear centrifugal clutch instead of a CVT or a multi gear shift on the go transmission.