vertical grimmace

My Feedback: (1)

So now that we can choose any .40 so long as it spins under 17,000 rpm which engine is the best choice? I have a Thunder Tiger but it never came close to 17,000. More like 15,500. I am thinkin' if I can have 17,000 I may as well and what would be the best choice?

BUDMAN27

What are all the other guys at your local club running in 424?

HighPlains

My Feedback: (1)

Your biggest problem is your altitude. At sea level you average about 29" of mercury for air pressure. As you gain each 1000 feet of altitude, you lose about 1" of pressure, so at 5000 feet you can expect an average pressure of about 24" of mercury. This means less power to turn the prop, somewhere around 82-85% of what you can make at sea level. Off setting this fact, the prop has less drag due to the thinner air. Summer heat, and humidity also lowers power.

But since everyone else is in the same boat...

TIA

Uuuuuuuuuuuuh, wha????

AH64DR

Our club when we were doing pylon races used Super Tiger ringed GS40's not sure what other club's rules may be. Also has your club restricted what exhaust you may run?

mikegordon10

Yep, just as AH64DR says, we did use Supertigre GS 40's and at 4400' above sea level. the guys that knew how to tune 'em had 'em turning a tad over 18,000 with a MA Scimitar 9 X 6 prop. There were also those who were cheating by running MA Scimitar 9 X 7's that were clipped a tad. OH NO, now I've went and let the cat outa the bag!

vertical grimmace

My Feedback: (1)

Now I could be wrong but I thought we were flying by the AMA 424 rules. No modified engine under a certain $ amount. The engine of choice for years has been the Thunder Tiger pro .40. I am sure it still is. With the contest provided APC 9-6 and %15 fuel.
I have not a actually attended an official pylon event for several years but I want to try to hit most of them this year. I need to get %100 current with the rules but I thought maybe you guys might have some insight into a little better engine.

P. Johnson

My Feedback: (1)

Some local races allow different engines, but the TT 40 Pro is the ONLY approved engine for AMA 424 at this time.

BUDMAN27

There you go boss.

fizzwater2

My Feedback: (61)

Where is this list of AMA approved 424 engines?

dwbebens

vertical grimace and others;

This discussion got me curious about the approved 424 engine(s).

I know that even fairly recently the AMA 424 pylon rules used to say that the TT Pro 40 was the only engine approved for AMA 424 racing. I absolutely know this. I looked it up a number of times just to make sure. Not only was the TT Pro 40 the engine of choice, but it was specifically stated to be the only approved engine for AMA 424 racing. I just now looked on the AMA site for 424 rules and I could not find any mention of the TT Pro 40 engine as being the only approved engine. There is no mention of the TT Pro 40 at all. What happened? Am I blind and just missed it this time? Did the rules change? The rules now mention the criteria of a $120 max street price, "take-off" rpm and "unloaded rpm" limits in order to be eligible for an "approved engine list" as determined by a committee. What are these RPM limits and where is this list?

It is my impression that this change seems to have happened since the AMA website format was changed recently. Is it just me or what???? WHAT HAPPENED???


Doug Bebensee

DonStegall

My Feedback: (1)

Doug,

The TT Pro 40 has never been in the actual core of the R/C Pylon Racing section of the rulebook. There was a web page with the Thunder Tiger Pro .40 as the approved engine. I haven't looked for it lately and the web site hierarchy has changed in the past year or so. It may still be under the Competition Documents section somewhere. I got the link from Steve Kaluf and I don't know what I did with it. I think it was an addendum with multiple tidbits for Pylon Racing. Or it may have even been on a preface page in the R/C Pylon Racing PDF file and I could be wrong.

One of the Contest Board members can probably tell us where to find it. Speaking of which ...

Dan Kane submitted the proposals that were added to 424 for the 2007-2008 cycle. As far as I know Jim Allen was/is the head of the 424 engine committee.

TIA

I'd like to know as well. Can a SuperTigre .40 be used, if not?

Jezmo

I took one of my Italian made ST GS40's apart this weekend because it turns a bunch more r's in the air than my China made G40's. The sleeves are very different and everything else looks identical. The transfer ports and boost port in the sleeves are significantly different. The transfers are larger on the Italian and the there is a divider in the boost port on the Italian engine that is not there on the China jobs. They turn a 9X7 about the same on the ground but the Italian one will unload much more in the air. The Italian motor will wax my TT pro like it's junk but the China motors are pretty close if you get the right prop on it. With a 9X6 APC on both the TT wins but with some prop selection I was able to get them very close. Bottom line the prop that worked best on the TT didn't work well on the ST and vice-versa. TT 9X6 APC and ST 9X7 APC was very close. (Stock mufflers on all)

gunfighter

My Feedback: (1)

HMMM... I have always understood that the TT Pro .40 was the only legal engine in AMA 424. It would be interesting to get some kind of "official" word on this!

DonStegall

My Feedback: (1)

Chuck,

While the TT Pro 40 has not been in the "core" rules, it has been listed as the only official 424 engine since the new engine list went into effect.

I have talked to Jim Allen at length about engines for 424. One of the main reasons the TT Pro 40 was settled on was because it was the most stable of the sport .40 engines. The ST GS-40 had known peformance enhancements that were hard to detect like a different crank that could be used. And from what I've read lately there were other things that could be done to it.

The TT Pro 40 can be enhanced as well with a piston/cylinder swap from a TT Pro 46. Some would say I should not even utter that. But enough people know about it that all contest directors should be aware.

The Magnum XLS 40 has been discontinued, as has the O.S. 40 FX. Thunder Tiger has ceased production of some of their two stroke engines. Hopefully the TT Pro 40 will continue to be made. I have no reason to believe it won't. In fact the price has risen as it seems that Thunder Tiger is aware that they have a captive audience.

gunfighter

My Feedback: (1)

OK - not to argue the point, but is this a "gentelmens agreement" or is the list actually published somewhere? And if it is, does any one have a link to it?

We seem to have several people asking the same question.

StanDouglas

There is actually a list. I believe it is the same as the APRA engine list. You can find that on the NMPRA website under "Racing Documents/"APRA Rules". I have no idea what happened on the AMA site. I guess it just fell through the cracks. Most of the various board members are probably not notified to review the AMA website upgrades.

In the next week or so I plan to make this information available on the NMPRA website and when ever possible link to the AMA site official information.

If there are other requests about official racing information please feel free to request it on the NMPRA website as I don't always check in here.

SD

sgilkey

My Feedback: (180)

I have Italian GS40s with divided transfer ports and non-divided. I have not been able to see a clear trend as to which is better, I've had "strong" and "less strong" specimens of each. Was not aware there was a "cheater" GS40 crank? Thought all GS40 cranks were the same?? Exhaust makes a big difference- the "Eco" muffler really strangles the engine, the swing are much better. The "standard" and "silent" swings seem to be about the same, the silent is a bit heavier but with the new weight rules that shouldn't matter much. Have never run a Chinese GS40 to compare with my Italian.

The TTPRO 40 has at least as many issues- aside from the breaking muffler thru-bolts and general difficulty of getting parts like that oh-too-easily broken off NVA, there's versions with beveled rods and square rods, ones with bigger crank gas passages, and of course the dreadful rear bearings. I don't really see how the TTPRO is much more "stable" than the GS40, and parts availability is a drag.

I've heard "tribal knowledge" that the TTPRO is the "only" 424 engine but have never seen that in any official way. I have heard some clubs allow the GS40 as well. I, too, would like to know what the real story is, are both engines allowed? Is the static rpm limit the "new" format, with any stock, under $120 .40? Hope this can be cleared up!

Scorpion Racing

AMA 2008 RC Pylon Rules
RCR16.3.2
6) Power output:
Sport Quickie is intended as an entry-level event for pilots who
are new to racing. Sample engines are tested via committee and a list of permissible engines is
published and updated as necessary, annually. Criteria include purchase price and power output
in both the normal takeoff RPM range and the presumed in-air (unloaded) RPM range. Any
engine with a tuned muffler is strictly prohibited. The cost of the engine must be below $120
(street price). If engines more powerful than this are to be used at a contest, the contest should be
sanctioned as Quickie 500 (Event No. 428), not Sport Quickie.
7) Prior approval of engines.
a. Procedure: All engines, past and future inclusive, shall not be entered into
competition until a five-member subcommittee of the RC Racing Contest Board has approved
the engine by an affirmative vote of at least three members thereof. Such approval may be given
orally, but shall be recorded for future reference. An engine shall be considered eligible for
competition if it meets all requirements of section 16.3.2.and, in addition, does not hinder
the state of this entry level event as determined by the aforementioned five-member committee.
The committee is appointed by the Racing Contest Board Chairman and will not include
any member with a vested interest in the sale or manufacturing of an engine for this event. In
addition, any engine can be removed from the list by an affirmative vote of at least three
members thereof.

I am sure I saw the TT40Pro as the only approved engine in the AMA sanction packet for my last race I held. I will check tonight if I can find it, or mabye someone with a sanction and AMA document packet for their race can look thru the loose sheets of paper for it. I believe it is a single 8.5 x 11 page with just a few lines of text on it.

Scorpion Racing

I found it! It is on a one page (front and back) titled:

BY-LAWS
OF
THE 5 MEMBER ENGINE COMMITTEE
Revision B.

Section 5 APPROVED ENGINE LIST
1. Thunder Tiger PRO .40

This is a sheet in the CD packet when you apply for a 424 event sanction. Stan, if you need this document for the NMPRA site, I can scan it and send you the document as a .PDF. Just let me know.