j_blaze

duration meaning it should be a taller hole right? maybe taller and thinner, how about an actual hole drilled out on the side of the skirt and not a notch. then we can adjust the size and timing, maybe?

lsurber

I would still use the radius cut because of strength and the fact that it is the only type of SPI port that is working properly on the above engine. This engine has been running great and refuses to stall with no high/low idle problems at all!

lsurber

Ok, degree'd the SH engine with erratic idle! Here it is!

Crank induction: open=210, close=40, Duration=190
Intake: open=100, close=260, Duration=160
Boost: open=100, close=260, Duration=160
Exhaust: open=90, close=270, Duration=180
SPI: open=328, close=32, Duration=64
Case Pos. Pressurization: Start=32, End=180, Duration=148
Case Neg. Pressurization: Start=180, End=328, Duration=148
Combustion Pressurization: Start=270, End=360, Duration=90

Notice: Look at the induction close point vs. SPI close and you will notice 8 degrees compared to 14 for the good engine! I will first increase Crank Induction close point to match that of the good engine then test. After that the only other change would be to extend the SPI duration. I will make these changes over the next week so stay tuned! We are almost ready to silence the critics!

I had to edit this post because I found an error, sorry!

SManMTB

Great! So now we can all get a video of 18 min run time on a tank.

lsurber

Once the timing issues are ironed out I would do this mod more because it REFUSES to stall even after extended high speed runs! Every other engine I have seen without this mod would stall when throttle is lifted after such abusive lean-out pulls!!!!!

The fuel economy is just a bonus!

Anthoop

[&:] A bonus to....less maximum power!
Be it noticable or not the mod will reduce engine power.
Quite often i see offers from companys(with dynos)letting you send a motor for testing,maybe it would be good but then all that talk was oohh pages ago.
Think i'll just stop posting here,just read and smile from here on in for me.

lsurber

I personally feel that most engines offer more than enough power to win races! This thread was started to learn about economy mods. There have been numerous threads on RCUniverse with questions on how to increase runtime! This mod has proven to me that it is indeed possible to get more runtime, sacrifice little overall power, and susbtantially improve the thermal stability of a modern engine.

Maybe you shouldn't post in this thread anymore if you are so negative and do not want to contribute anything worthy![:'(]

j_blaze

i don't have a dyno but i think i had an increase in power. i can land the buggy in spots i could only land it with 30% with high temps. it could just be the engine coming alive on its third tank now or the different piston sleeve. now with 20% it can get there and stay cooler, just gotta figure out the quitting.

duckedup

The head button mod? attached are couple pics of what it looks like (one persons version)... I only did one cut on mine, though, and it faces the exhaust port (still kind of experimenting with it..) I've read you can face it towards the boost, or the exhaust, or both - just like everything else, not everyone agrees, so it's trial and error for me! lol..


This seems like an interesting mod here (economy mod), I'm looking forward to reading more feedback [sm=thumbup.gif]

lsurber

The headbutton mod probably has more to do with reducing compression than it does directing burn.

I am almost there Blaze! I believe by next week I will have a fix for the erratic idle. It will probably involve using a degree wheel and modifying crank induction timing! Do you feel up to it?

It would be a good idea if you were to degree your engine and post results here. The most important measurements are crank induction and SPI timing marks.

j_blaze

i did one big port to the rear too, seemed like it would do more good on the way out than in. degree my engine? that is way too advanced for me right now but i'm guessing you start at tdc or bdc and measure at what degree stuff happens in the crank and what not. i'll give it a shot, i'm game, i've got nothing to loose, its only metal right?

lsurber

Get yourself a degree wheel, fix it to the flywheel, make a pen mark on flywheel at TDC=0, then turn crank till crank induction port just starts to open. Record your results and repeat for crank induction close point. Do the same for the SPI timing. You don't really have to worry about the exhaust or intake port timings.

lsurber

Here is a degree wheel from another thread! I don't like it because I prefer measuring everything from TDC=0,360 but this will work fine. It just takes patients and being very careful. It is common to see measurements like ATDC, BTDC, BBDC, ABDC where A=after and B=before. I don't like this method because it cannot be used in a database to perform calculations without interpretation of the numbers.

Another solution would be to get a school protractor and drill the hole to fit the output shaft.

tonyedge540

retarding the timing does increase fuel economy but you lose performance even if you mod it to compensate you still won't have the performance before you moded the engine i mod engines to and you need to increase air volume and fuel to get power it just how 2 stroke works if it was a 4 cycle than you can do more because it burns cleaner

lsurber

I have more need for fuel economy than for power! I have other mods for power that almost throw the tires off the rims....!!!!! This mod has proven mileage benefits but a few timing issues which I will have worked out by late next week. I have one good engine for which I have posted complete timing profile on preceeding pages. This engine has performed very well with minimal power hits, excellent mileage, and extremely good thermal stability(no lean-out stalling under severely sustained high speed runs).

j_blaze

i had the toki 21 spi out today and it ran great, temps were high but a bit of richening got them down. its cooled down last couple weeks down here in fl, still crazy quick. it ran great on grass and gravel and the quiting went away, thats with a HUGE spi port too. the crazy low idle seems to be gone too. its more of a slow decrease of rpm's, 20 seconds or so, then it quits. kinda like a normal engine. i'll have it on the track tomorrow to see how the jumping affects the quiting. i ran this fuel tube configuration about 1 gallon with another engine and had no quits. we'll see. power is still there but topend seems to be slightly reduced. my truggy runs a bit faster on a long straight right now. with a modded non-spi 27 on it.

j_blaze

wow, has it been so long already? seems like just yesterday i was posting on here. anyways, back to doing my spi's, about 15 motors later. i did it to a sts t21e with about a gallon run through it. best run time i could get was about 8:30. i decided to spi again since runtime is winning races out here, and 10:00 is the magic number. took out the motor today and broke the 13:00 minute mark on a very dusty track in my rc8t. with traction it could be more.