ESE's works engine tuner

[jamathi]

Why your cil.is stil on the shelf by Harm Frits

Yes, why?? Is nobody interested in trying it?
I am very curious to see if it works or not....

[Frits Overmars]

Yes, why?? Is nobody interested in trying it?
I am very curious to see if it works or not....

That is not the cylinder we are working with, Jan.

[dutchpower]

Still its on the shelf Frits Both !!!!!

[41juergen]

A friend of mine has built a NS500R with a tuning kit from DMR out of Japan. The bike is equipped with Jim Lomas pipes, has the stock CDI and the stock reeds / carbs / air boxes. During first tests on the dyno the exgas temps (200 mm behind piston face, measured with a 1,5mm type K thermocouple) raised up to 620°C at approx. 9000 rpm and an AFR of approx. 12,7. So he was afraid of too high exgas temps and went richer on the mains until reaching an AFR of approx. 11.2! BUT the exgas temps were not decreasing, not 10°C. So we checked the stinger diameter and found an inner diameter of 22 mm, that with a measured power of approx. 66 rWHP (measured on a Dynojet). I have put that project into EngMod and the prediction is approx. 36 crank HP per cylinder, (so only a mid bmep) ending up with approx. 108 HP.
So any idea why the exgas temps are not decreasing when going rich?

[Tim Ey]

Hi Jürgen,

with a 1.5mm thermocouple sitting 200mm behind piston face, 620°C is not alarmingly high for my gut feeling.

Where do you measure AFR?

As a first guess what might be wrong: I would check the ignition timing.

[41juergen]

Hi Jürgen,

with a 1.5mm thermocouple sitting 200mm behind piston face, 620°C is not alarmingly high for my gut feeling.

Where do you measure AFR?

As a first guess what might be wrong: I would check the ignition timing.

Hallo Tim, the problem is not the 620°C at 9000rpm, the problem is that the temperature rises further on until 11000 rpm up to 700 °C. And the strange thing is, that going bigger with the mains the temp does not go down (he started with one size bigger, than a next bigger until AFR reached 11.2). He is using Bosch wide band sensors , getting the exhasut being sucked through a copper pipe being inserted through the silencer and the stinger into the pipe. We did a back to back test with my data logger having the lambda sensor mounted approx. 300 mm behind the piston face showing very close results in lambda.
The igniton curve is the stock NS400R one, having 15°CA at 10000 rpm and 12°CA at 11000 rpm...

[Frits Overmars]

...The problem is that the temperature rises further on until 11000 rpm up to 700 °C. And the strange thing is, that going bigger with the mains the temp does not go down (he started with one size bigger, than a next bigger until AFR reached 11.2). He is using Bosch wide band sensors , getting the exhasut being sucked through a copper pipe being inserted through the silencer and the stinger into the pipe.

Maybe that copper pipe creates too much of a restriction in the stinger.

[wobbly]

The issue sounds like a combination of factors.The probe is too far into the header for a start. 3X bore from the piston face is the rule of thumb , and the probe must be an exposed tip and sitting exactly on
the header centerline. Having a short probe down the header will absolutely read high.
Pulling more timing out past peak Hp makes the egt continue to rise , and you end up using fuel to cool the temp , rather tha make power.

The way to fix this is to retard only enough as is needed just past peak , then flat line , this stops the egt continually going up.
If it wont rev without a heap of retard the pipe is too long - and a better way to make it rev is a solenoic powerjet.

The only place that gives reliable Lambda readings without affecting the backpressure is at the beginning of the muffler .
I weld a fitting onto the muffler can , with an extended tube the OD of the perforated , and scallop the tube end to sit over the perf tube.
Then the Lanbda sits in this " pocket " fed continually thru the perf holes.
Going thru the stinger into the pipe makes a joke of the work done in EngMod tracking the Mach in the tube to optimise the area.

[41juergen]

Wob, to make sure I understand correctly: the temp measuring probe sits 200 mm behind piston face (with a bore of 66mm that should be ok, right?) and of course in the centerline (learned that at the company when doing some test 25 years ago )
My friend did tests with and w/o the copper pipe in the stinger with no significant effect (in power and temps). However, my guess is still the stinger, even it has a 22 mm diameter.

But the most courius thing for me is: What else could be a reason that when going bigger with the mains no change in EGT can be seen?

Regarding the probe position for the AFR measurement, I did a test on my bike having one sensor approx. 250mm behind piston face (in the header), the other as you mentioned in front of the muffler in a short pipe with a slightly bigger diameter (to get the same free cross sectional area), unfortunately the battery had not enough power to heat both sensors, but up to where the heater stopped the signal were pretty much the same...

[katinas]

Hi, juergen

NS 400 stock ignition timing curve is too advanced for correct squish height ( 0.8 mm /1 mm). Std NS 400 squish from factory variate from 1.8 to 2 mm with aprox 15,5 cc head volume with plug hole.
I dont know exactly, but DMR cylinder heads volume looks like too small, with very wide squish band.
Some time ago, when I started endless testing with NS engine, first things was to correct squish height to 0,9 mm and 13.5 cc volume with std cylinders and heads. And gains in upper range, comes only after retarding std ignition with additional plate (add photo ). Very important too harmonized ignition and new 500 cc set up before goes deeper. But of course first thing after 500 cc kit, must be zeeltronic or ignitech ignition. They made nice special kits for NS 400.

Very interesting about head volume on 500 cc kit.

[Condyn]

Do you guys think this pipe would be worth a try? My target peak rpm is 10,000. This is a vintage piston port, single exhaust port, 450cc parallel two cylinder snowmobile engine with a CVT. Exhaust duration is 202° with 35° blowdown. I have physically built 6 sets of pipes for this particular engine thus far and they are all worthless. None look anything like this pipe. Some longer, some shorter, most fatter. Based on the minimal info I am providing, is there anything with the design that stands out and screams “you are wasting your time!” Normally I would just build them, and try them, but my ego is already dwindling at this point.

[andreas]

I'll venture a suggestion. The pipe starts at 45, if this is because the duct ends ,and will always do so, at 45, fine. If the duct size can be altered, it seems to me that this 225 cc single port will work better with about 40 mm d0. The diffuser is nice and shallow, maybe the d max can be reduced even more, who knows. Variable transmission, consider a steeper baffle, perhaps a multi stage.

[Condyn]

You are right. The d0 is a screw up on my part and I will correct that. It is supposed to be 41mm. I did that on this pipe only because It uses slip over pipe flanges with spring mounts. The large 50mm OD of the flange makes it a little more time consuming to make the slip joint. So I was foolish and enlarged the d0. I understand that was improper. I will correct it and maintain the header angles. You think my diffuser proportions and angles are feasible, and in the right approximation? As for the rear cone, I could extend the dwell and make the baffle steeper. Something like 23°? Thanks for the suggestions.

[andreas]

Yes 23*, possibly up to 30*. It's easy to go back if it doesn't work, remember the reflection point "pivots" maybe 3/5 down the cone, not the absolute end.

[wobbly]

Condyn everything is wrong with the design - send me the pack file . PM me for email.