ESE's works engine tuner

[jonny quest]

When the RSA went to unleaded fuel I understand after engine was adjusted for this fuel peak HP went up slightly.

What happened to lower rev range? Do it suffer slightly compared to the high compression leaded engine?

[Frits Overmars]

The RSA never went to unleaded fuel Jonny. Grand Prix Motorcycle Racing went to unleaded fuel long before the RSA was born.
Let's talk Aprilia RSW then. These ran a 19,5:1 compression ratio on 130 octane leaded fuel. When the stuff was banned, they initially ran a 14:1 compression ratio on unleaded, which made the engine lose bottom power but at the same time let it rev more freely to the pleasure of the riders. Then the compression ratio was gradually restored to 15,5:1. At the same time other paths of development were explored, so after a while the unleaded power was better than the leaded power had ever been.

[TZ350]

TeeZee , having done tons of work using Meth before I had grey hair , I wonder mainly why you are using Meth as an aditive to petrol. By far the best results for an air cooled is to maximize the natural cooling effect of huge amounts of rich Meth mixture going thru the engine. Using 90% Meth , 5% Acetone , 5% petrol means you can run identical com to Avgas as you would in a water cooled cylinder , and have no heat soak related power loss.

Thanks for your reply. When I first ran 100% meth the engine ran to cold to evaporate the fuel properly for good air/fuel mixture. It was so cold and leaner the more meth I pored in. Wound up so rich raw fuel was dribbling out the stingers. Bore wear from the bore wash was dreadful too. Ran warmer and better with 50/50 mix of meth and acetone.

The current approach of starting with 25% meth is to more scientifically with trial and error keep adding meth until I get the balance right between engine temp and heat soak. The bike will also have a head temperature sensor that adds fuel when the engine gets above a pre determined level. Again trial and error.

... but you must have a cold ( 11 ) plug and as much grunt as you can get with the ignition if running +20% rich with high com. Now days this is easy , run the ignitech at 14.2 charging volts and parallel up the outputs of a DC CDI P2.

I was unsure about this part, hotter or cold plug with a cold meth setup. Thanks for confirming the plug heat range. I have a good handful of NGK 9's and 10's but no 11's or 12's and they are expensive and harder to get.

I have one new really cold surface discharge plug. They are more available than 11's and 12's. Before I get any more, would surface discharge be Ok?

... Now days this is easy , run the ignitech at 14.2 charging volts and parallel up the outputs of a DC CDI P2.
I used a huge Crane ignition coil designed for CDI use in NASCAR race engines as it has the only two things that will increase spark energy in a DC CDI , very low primary resistance and high inductive reactance. This setup pulled nearly 5 Amps from a P2 that previously ran at around 1.5A on a normal single coil - a massive increase in ionisation and burn time energy. Do it right and 16:1 is a walk in the park for your application.

Thanks for confirming the com ratio possible. my 15:1 should be good. Interesting about the DC CDI P2 and the Crane coil. I was planning on using a P1 I brought from FastBike gear. I guess I will be getting a P2. Unfortunately they use different looms so it is a re wiring job now too. And I will have to re jig the charging system so that the voltage rectifier/regulator with capacitor holds output at 14.2 Volts at 5 Amps.

If I am going to run a P2 I was wondering about using one of those old twin plug heads. You know the kind that were popular in the 70's so that the off road boys could have a hot and cold plug and burn holes in their pistons. Because they did not understand that a hot plug was hot regardless if it was the one sparking or not.

Would a Hemi chamber, squish and firing two plugs be worth while power wise?

Wob. Thanks for your help and encouragement.

[wobbly]

I ran 90/5/5 for years in the MX only 125 National ( water cooled TM/Husky ) class karts , with many National titles and lap records.
Never had any issues with it being too cold or over fueling out the stinger - it ran 19:1 with a normal race petrol ignition curve , and the carb was jetted calculating 2.2 X the area of petrol
1 - pilot jet , 2 - std needle parrallel with drilled tube , 3 - drilled tube/ needle end annulus thinned at WOT and 4 - main jet area , split into 3/4 area of jet + 1/4 area of screw adjustable PJ.
This ran best at 800*C and no more than 1/8 turn on the PJ was ever needed to keep it there on the fly - but the pipe was very much shorter.
Running the Mega ignition setup a surface gap would be great - always wanted to but never tried that.
A cold plug is needed running the super high com setup as I believe the actual burn temp in the chamber is super high , even thou a ton of fuel is dumped into the pipe.
Using a 10 plug the exposed body would over heat causing pre ignition and holes in the piston.
I have tried a twin plug setup in a CR250 - made no difference at all - the chamber shape in a 2T is damn near perfect in any form for max flame front propogation.
Will send coil asap if needed.

[speedpro]

If you suspect problems with over-cooling could you shroud the engine and limit air flow to the fins?

[Grumph]

i've quoted it here before - but the only experience I've had with a surface gap plug could at least have been worse.
Stinking hot day at Ruapuna - over 30C - and my Mach 3 ran on when I came into the pits.
Under stress the plating on the plug faces had lifted and the slivers of plating became a glow plug.

If i used one in extreme circumstances as you propose, i'd take a light cut off the faces in the lathe before use. It's only a cosmetic layer.

[TZ350]

... ran best at 800*C and no more than 1/8 turn on the PJ was ever needed to keep it there on the fly - but the pipe was very much shorter.

I understand the need for a shorter pipe when running meth. But 800*C ? is that 800*C in the pipe EGT or was that meant to be 80*C ECT engine coolant temperature?.

[wobbly]

Sorry TeeZee that was a typo , should have been 800*F EGT in the header.
The engine on petrol was 1260 * F and was hard to keep at 120* F water temp , but on Meth it ran at 100 all day.

[jonny quest]

Latest generation Honda CR125. Right side crank seal pops out randomly.

Cases are in good shape, I've tried using 3m bond 1211. Didn't help. I know my piston ring is ready for a change, but it's not horrible... could that be the cause?

Suggestions for a bonding agent? I really don't want to use a punch and peen cases.

[Larry Wiechman]

Latest generation Honda CR125. Right side crank seal pops out randomly.

Suggestions for a bonding agent? I really don't want to use a punch and peen cases.

Three #6-32 Button Head Socket Cap Screws arranged in a bolt circle pattern that positions the heads to overhang the seal bore diameter.

[TZ350]

Sorry TeeZee that was a typo , should have been 800*F EGT in the header.
The engine on petrol was 1260 * F and was hard to keep at 120* F water temp , but on Meth it ran at 100 all day.

Great, thanks. I was wondering about ECT and EGT.

So I could get my head around the values I did some conversions to *C.

800*F EGT = 427*C
1260F EGT = 682*C
120*F ECT = 49 *C
100*F ECT = 38 *C

Thanks again, now I know what I am looking for.

[jamathi]

The RSA never went to unleaded fuel Jonny. Grand Prix Motorcycle Racing went to unleaded fuel long before the RSA was born.
Let's talk Aprilia RSW then. These ran a 19,5:1 compression ratio on 130 octane leaded fuel. When the stuff was banned, they initially ran a 14:1 compression ratio on unleaded, which made the engine lose bottom power but at the same time let it rev more freely to the pleasure of the riders. Then the compression ratio was gradually restored to 15,5:1. At the same time other paths of development were explored, so after a while the unleaded power was better than the leaded power had ever been.

The 'unleaded' power was better than the 'leaded' within 3 month's, mainly because a much better combustion chamber was used. There was no power loss at low rpm, and much better overrev... And spark plugs no longer cracked...

[jonny quest]

Was a lower compression head tried with leaded fuel?

Or, because "thermodynamics " says 18:1 is best... let's build everything around that and not make it a variable

[wobbly]

Simple really - the engine made best power at 19: 1 , at 18:1 it never made more even with added advance.
There is always a narrow window of variables that work in synergy with the fuel characteristics , and everything is arranged to extract the max power without detonation causing the need to compromise
egt or advance just to control this issue.
Its also amazing as Jan alluded to , is that the chamber shape shows big changes in performance with samll changes in geometry.

[sniemisto]

14mm stinger is very small.
For a 50 cc I never go below 16 mm

I'm back on this Derbi project. I haven't fixed yet the issue with low EGT on dyno. I got 10ml burette for compression volume measurement, I'm going to measure it soon.
We had race last weekend and I was forced to deal with exhaust and stinger first, as I had EngMod developed pipe plans to make more power. Other pipe dimensions changed at same time, so its not pure stinger diameter comparison. My last pipe had 14mm venturi and this new is straight 15,9mm without venturi.

I got good drop on EGT, it went down to 630*C on long wot run, as it was 670-680*C with smaller stinger. I was able to jet down main from 128 to 120 and ended up with 670*C. Bike was nice to ride with wide power and it was able to go on higher gearing that it used to before.



Next I will proceed with compression ratios.