GT engine rules ?
 

So who are the individuals who are responsible for the current GT engine rules ? what does everyone think of these rules ? 5 port with 7 mm insert .... what was the purpose of these rules and did the rule achieve the desired purpose ? I have my own opinions of these rules that I will share later, but for now I want to find out who made up these rules and if anyone thinks these rules were effective and beneficial to GT racing or possibly feel these rules were arbitrary , ineffective and detracting from GT racing.... FYI a 7 mm insert can reduce engine output by as much as 20% and increase internal wear and tear...

Engine rules should be made or advised by people who have knwowledge of engines.

The 5 port rule with a 7mm insert is I believe mainly a cost rerduction so no high end 9 port engines can be bought. But nothing is sayd about the internal timings and modifications. So you have a cheap 5 port engine and then you buy a set of ceramic bearings and let it be modified by someone making it a total price of a 9 port engine.....

EXACTLY!! i dont understand the logic behind that:confused:

a 7mm restricor is not going to reduce output 20%?? who told you that? and why would it create less wear and tear?

The 7 mm sure does reduce output ...I am one of the few who actually owns and operate a Nitro engine dyno and have tested inset extensively ..and yes a 7 mm insert drastically reduces power , in some engines it can be more then 25% loss as opposed to a 9mm.. even in a lower timed offroad engine the losses are quite big and of course in a higher timed onroad the losses are even more....

The wear and tear comes from the engine being choked back and being forced to run leaner in an attempt to make power.. As well the choking the engine back narrows the tuning window and increases the likelihood of running lean

The engine rules were very foolish and not well thought out and have done nothing towards making the class any more affordable, all they have done is needlessly slowed the class down and taken away some of the excitement and thrill.. In the grand scheme of things the racing is no cheaper and the cars are needlessly hobbled so these rules need to repealed and the class allowed to run at its full potential.

Anyways who came up with these rules ?

As you might have noticed I am not a fan of needles arbitrary rules, especially in motorsports..for some reason these RC sanctioning bodies seem to get carried away and tend to make some very shortsighted rules that have very big and substantial negative consequences to the sport...

Most in Gt were running 8mm venturis not 9, all 9 does is give you poor mileage in a heavy car. So you are saying going from an 8 to a 7 nets you a -20% power loss??

If a smaller venturi equals less wear and tear then why is it that offroad engines dont last nearly as long as onroad engines do?

no matter what size venturi you use the engine performs best at the exact same A/F ratio. yes you have less air entering which equals less fuel which equals less castor oil for protection but as forementioned on road uses at least 2% (sometimes more!) oil for protection and lower nitro. Technically a smaller venturi could actually give more wear and tear! I dont think venturi size determines how long an engine is going to last one way or the other, especially only 1mm.

I agree with you on the rules, would love to hear the true logic behind this because as we have all seen that it makes no difference at all. a Modified MITO is every bit as fast if not faster than a 9 port with 8 or 9mm venturi!

Not sure if you have been to a national level GT race lately but they are very bit as fast if not faster than they were with open engines. and thats because as Roelof said earlier guys are just buying a cheap ison ,installing ceramics and having it modded to make more power than before with good if not better gas mileage. When a 5 port /7mm gets the same exact pit time as a 9 port, that tells you something right there!

2 reasons:

1) Offroad engines do not rev that high as GT and onroad.
2) Most specific offroad fuels have a higher oil content.

we are "supposed" to use offroad 5 ports........ which would be the same RPMs:lol:

VP 30% nitro only has 9% oil
VP 25% nitro has 11%

you are very wrong to think that a engine will make its best power on a 7mm insert..... 7 and 8 mm do not make as much power as a 9mm........ as well the power drop off from 8-7 mm is much bigger then you realize, just 1 mm can result in as much as a 20% loss of peak power as well as a substantial loss in peak RPM ...and yes the 7mm venturi makes the tuning window narrower and the engines will end up on average having shorter lifespans...all the rules did was slow the cars down and the racing is no cheaper then it was before

I never said it would make its best power with a 7mm, thats not what i meant but a modded 7mm can make more power than a non modded engine with a larger venturi. I have seen it first hand:nod:

i have a hard time seeing a 1mm rstriction equaling 20%, you have a dyno sheet to verify this?

We will agree to disagree on the lifespan subject....

The rule did not slow the class down at all. Last race i had a very hard time keeping up with a modded MITO, in fact he had more top end than i did with a non modded 9port/8mm. before the rule most did not bother modding engiens we just all ran 9ports but now if you want to keep up with the elite you have to have a modded 5port which is faster! At least thats my logic and what i have experienced here lately anyway!

If you think the amount of ports is determing the performance then think again....

what pipe are you guys running ? 2 chamber or 3 chamber ? this can make a huge difference.. Are you using INS boxxes ?

now when you say modified and stock , would you consider removing head shims modifying ?

Power and efficiency are closely tied and often times when engine is making its best power its also running most efficiently ..when we start forcing less then ideal conditions on the engine you will start to see a reduction in fuel economy .. Does your daily driver get better fuel economy with a partially clogged air filter ? 2 strokes are funny and I am finding that when I hit the magic spot power wise on a modified engine we are also seeing extremely good runtime as well....now what has to be taken into account here is that when a engine is making more power it is also capable of doing more work, which can change the runtime.... what I am getting at here is that comparing runtime between a fully modded 9 port on a 9mm against a choked back 5 port may not give the full picture...the modified fully opened up 9 port can be getting better efficiency but doing more work in the same amount of time as the less efficient 5 port , so their final runtime looks the same ..meanwhile the 9 port is cutting faster laps and hitting 4 MPH higher down the straight....

I am fully willing to dyno test any combo someone wants me too...just let me know the engine and pipe, or send me your engine and pipe...

9886 and short header modded straight or conical

yes INS boxes


I understand exactly what you are saiying but at the end of the day its about what happens race time and on the track. we all were coming in within a lap of each other. my car was second fastest over all of the other 5 port by alot actually (picco, ison) while the modded Mito had me by a few mph. My engine is not modded at all.

I would like to see this 20% loss that you mentioned earlier though, where are you getting that from? i assume your dyno right?

when i say mod I mean port, polish etc etc

I know , hence the :lol::lol::lol:

Which goes back to your original statemnt about how only those who know about engines should make engine rules!!

OK...

I have been at several EFRA AGM's and the EFRA wants to lower down the noise for years. Something they are failing for many years by approving loud noise exhausts. But with one AGM they come up with 2 thoughts to lower down the noise in the future:

1) forbid AAC engines because the aluminium sleeve is making more noise.
2) max 5 port engines because less ports is making less noise.

Both to my knowledge picked out of nothing. I asked if they can show me a test based on 2 same engines with one AAC and the other ABC, they could not. Also as I was running modified 5 port engines I shared my knowledge that my 5 port engines were not making less noise than 7 and 9 port engines.

These thoughts of the EFRA never came back on the agenda, but it shows how stupid organisations can be.....

This pipe is not legal 9886......has not been for a while.

DJ Apolaro