GX35 Honda 35cc 4stroke

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ol boy
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GX35 Honda 35cc 4stroke

Post by ol boy »

Ran a gx35 Honda single cylinder 4 stroke on full sequential using the map sensor as can input. Its amazing how well it will run when the injector phasing is tuned correctly. Swinging a 4-1 flying magnet crank wheel. This thing will.swing a 17x10 prop to 7500rpm. Ms2extra 3.3.2 code.
306 SBFord, Torquer II EFI intake, 60 lbs injectors, 8 LS2 coils, VS Racing 7668 turbo, 4R70W, MS3x fw1.4 w/built in trans controller.
24c
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Re: GX35 Honda 35cc 4stroke

Post by 24c »

ol boy wrote:Ran a gx35 Honda single cylinder 4 stroke on full sequential using the map sensor as cam input
That's good to know, well done. :)
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Re: GX35 Honda 35cc 4stroke

Post by racingmini_mtl »

Do you have more information on the rest of your setup? That prop and RPM sound like that would result in a healthy thrust.

Jean
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ol boy
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Re: GX35 Honda 35cc 4stroke

Post by ol boy »

I work for a small company hfeinternational.com, we do efi conversion for UAV companies. A local customer needed to get more power out of this Honda 35. We removed the massive flywheel that was used to produce the energy for the spark output. That freed up a pound of weight and we gained 200 more rpm. We are now driving a rcexel ignition box from our ecu. We were only going to do a spark only conversion and tune the walbro carb for max rpm but I got board last week and stabbed on a 3d printed TBI made from PEEK. We found some really small injectors that only flow 15ml/min at 10 psi. The ecu controls throttle position with a micro digital servo that's mounted to the TBI.

I'm planning on being at the megameet this year with some of the MS related products to show off. I'd like to bring an engine to demo on the bench.

This thing will fly a 40lbs plane. Makes 25ish lbs of thrust.
306 SBFord, Torquer II EFI intake, 60 lbs injectors, 8 LS2 coils, VS Racing 7668 turbo, 4R70W, MS3x fw1.4 w/built in trans controller.
racingmini_mtl
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Re: GX35 Honda 35cc 4stroke

Post by racingmini_mtl »

Nice! Thanks for the information.

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PierreL
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Re: GX35 Honda 35cc 4stroke

Post by PierreL »

ol boy wrote:Ran a gx35 Honda single cylinder 4 stroke on full sequential using the map sensor as can input. Its amazing how well it will run when the injector phasing is tuned correctly.
Ryan,
As you know i'm setting this on my engine too.
I did some tests to figure out the injection phasing
At +- 2500 t/min (high speed idle), i concluded that the best angle was around 200° (see http://www.msextra.com/forums/viewtopic ... 34&t=55054))
Now i'm going to try to create a table for different rpms, and WOT.
Now my questions ?
- Did you also make a table ?
- If so, how did you set the table up ?
- I found that phasing had a big impact on AFR at iddle. (from 13.4 to 11.6 afr). But will it be the same difference at wot?
Thanks,
Pierre
ol boy
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Re: GX35 Honda 35cc 4stroke

Post by ol boy »

I set the end of pulse around 200* in the lower rpm range and reduced it to 160ish around WOT. I'm sure these numbers will change with the duty cycle of your injector and the length of the intake runner. The idea is to find the richest ego reading when moving the phasing around then lean out the VE table to get the AFR you want. I was seeing 60% duty at 6600 rpm and the distance from the injector to intake valve was about 6 cm. Our TBI also had too large of an intake tract as it was designed for a 57cc engine and not a 35. The 35 intake hole is only 10mm while the TBI was 15ish or bigger.

What psi are you working with for fuel pressure. We found an injector that will flow 17ml/min at 10psi. It foot print is quite small too.

Later. Ryan
306 SBFord, Torquer II EFI intake, 60 lbs injectors, 8 LS2 coils, VS Racing 7668 turbo, 4R70W, MS3x fw1.4 w/built in trans controller.
PierreL
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Re: GX35 Honda 35cc 4stroke

Post by PierreL »

ol boy wrote:I set the end of pulse around 200* in the lower rpm range and reduced it to 160ish around WOT. I'm sure these numbers will change with the duty cycle of your injector and the length of the intake runner. The idea is to find the richest ego reading when moving the phasing around then lean out the VE table to get the AFR you want. I was seeing 60% duty at 6600 rpm and the distance from the injector to intake valve was about 6 cm. Our TBI also had too large of an intake tract as it was designed for a 57cc engine and not a 35. The 35 intake hole is only 10mm while the TBI was 15ish or bigger.

What psi are you working with for fuel pressure. We found an injector that will flow 17ml/min at 10psi. It foot print is quite small too.

Later. Ryan
Good. So we are in the same situation: i also set the end of pulse at 200°.
At 2500 rpm iddle, my PW is +- 2ms.
with 0,7 ms of dead time, "real" injection duration is +- 1,3 ms
At 2500 t/min the engine truns of 15° each ms.
So i assume that the fuel begins to flow out of the injector 1,3*15 = 19,5°
So fuel starts to flow out 219.5° and ends at 200°.

If i'm right, at that time, valve is open, and the fuel mix with the air and enter directly in the head.
So what i'm wondering now is: why are these 200° the best moment ? What is the goal ? I'm a bit surprised, because i was expecting that the best thing would be to inject when the valve was still closed and evaporate the fuel.
What do you think about it ?

(i'm working with 2.5 bars injection pressure, but i will go to 4 bars because then the fuel will be more finely atomized. My injector is a Yamaha scooter one. It is a little bit too big: 44cc/min. In the past we used smaller injectors from FC-Design company in japan, but had a HUGE LOT of leakage problems)

Pierre
ol boy
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Re: GX35 Honda 35cc 4stroke

Post by ol boy »

So what i'm wondering now is: why are these 200° the best moment ? What is the goal ? I'm a bit surprised, because i was expecting that the best thing would be to inject when the valve was still closed and evaporate the fuel.
What do you think about it ?
Spraying the fuel just as the intake valve has opened gives it time to enter the port and saturate the surrounding air. When the intake valve opens the majority of the intake stroke will be this saturated air charge. If your end point is at 200* then you are spraying right as the valve begins to open which is around the 160* mark. Your timing angles are start at 180.5*+ 19.5* = 200* end point.. The sooner the fuel is pulled past the intake valve the less time it has to stick to the walls which would require more fuel to get the proper air/fuel charge.

Your duty cycle is really low, around 2% at 2500 rpm? I'm only running 10 psi (0.7 bar) fuel pressure, the fuel leaving the injector nozzle will be at a much lower velocity and needs more of a head start.

How are you measuring EGO feed back? We are using a Horiba emissions analyzers to read the 5 gases. The idea is to change the phasing to achieve the highest (richest) mixture, which requires you to pull fuel out to get back to the desired AFR. This becomes the most efficient injector timing angle.
306 SBFord, Torquer II EFI intake, 60 lbs injectors, 8 LS2 coils, VS Racing 7668 turbo, 4R70W, MS3x fw1.4 w/built in trans controller.
PierreL
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Re: GX35 Honda 35cc 4stroke

Post by PierreL »

ol boy wrote:
Spraying the fuel just as the intake valve has opened gives it time to enter the port and saturate the surrounding air. When the intake valve opens the majority of the intake stroke will be this saturated air charge. If your end point is at 200* then you are spraying right as the valve begins to open which is around the 160* mark. Your timing angles are start at 180.5*+ 19.5* = 200* end point.. The sooner the fuel is pulled past the intake valve the less time it has to stick to the walls which would require more fuel to get the proper air/fuel charge.
Sorry, i but i do not completely agree.
In the MS docs you can read: "Timing for fueling is worked out the same as ignition, in that a positive number is Before Top Dead Centre (BTDC), but only for the compression stroke! So we have can have up to +360deg (Before TDC of compression) and -360deg (After TDC Compression)" (http://www.msextra.com/doc/ms3/sequentialfuel.html)
So, if i'm not wrong, injection begins at 219.5 and ends at 200.
Which means that we are at the end of the intake stroke, not the beginning. Don't you think so ?
And if it is the case, what is the meaning ? Why are we richer when we inject at the end of intake ?

We use a simple innovate LC1 wide band lambda sensor ...

Thank you again for your feedback,
Have a nice day,
Pierre
ol boy
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Re: GX35 Honda 35cc 4stroke

Post by ol boy »

Uhm... Looks like I had the layout in my brain way wrong. I don't have this motor on the test bench any more to try the negative phasing numbers. Even when running other motors in batch mode I would spray fuel just after TDC to catch the beginning of the intake stroke.

Have you tried -200 yet?
306 SBFord, Torquer II EFI intake, 60 lbs injectors, 8 LS2 coils, VS Racing 7668 turbo, 4R70W, MS3x fw1.4 w/built in trans controller.
PierreL
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Re: GX35 Honda 35cc 4stroke

Post by PierreL »

ol boy wrote:Uhm... Looks like I had the layout in my brain way wrong. I don't have this motor on the test bench any more to try the negative phasing numbers. Even when running other motors in batch mode I would spray fuel just after TDC to catch the beginning of the intake stroke.

Have you tried -200 yet?
Yes, i did try from -360 to + 360.
You can see the result on the second image of this post: http://www.msextra.com/forums/viewtopic ... 34&t=55054
+200 was better than -200
Unfortunately the image is not complete: +360 (just after tdc) is not displayed, but it was not better than +200 ...
I still can't figure why ...
ol boy
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Re: GX35 Honda 35cc 4stroke

Post by ol boy »

The only thing I can think of is the fuel is sprayed into the intake runner at it's hottest point(right at TDC Compression/power) or there abouts, which help vaporize the fuel as it sits near the intake valve. It's been talked about in the forums that the OEM's do this for emission reasons at idle then move the injector phasing to favor the intake stroke timing at higher loads and rpm. We have a small AC motoring dyno for small engines that allows us to load the engine at any rpm. We then work our way up and down each load cell and tune the hole map. For the Honda I just did the quick and dirty test using a prop. The phasing may change from lower load to higher loads at the same rpm.

Can you solve for what velocity the fuel would need to leave the injector to cover the distance from the injector to the intake valve for any given RPM? Maybe it really needs that much of a head start...? :roll:
306 SBFord, Torquer II EFI intake, 60 lbs injectors, 8 LS2 coils, VS Racing 7668 turbo, 4R70W, MS3x fw1.4 w/built in trans controller.
PierreL
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Re: GX35 Honda 35cc 4stroke

Post by PierreL »

ol boy wrote:The only thing I can think of is the fuel is sprayed into the intake runner at it's hottest point(right at TDC Compression/power) or there abouts, which help vaporize the fuel as it sits near the intake valve. It's been talked about in the forums that the OEM's do this for emission reasons at idle then move the injector phasing to favor the intake stroke timing at higher loads and rpm. We have a small AC motoring dyno for small engines that allows us to load the engine at any rpm. We then work our way up and down each load cell and tune the hole map. For the Honda I just did the quick and dirty test using a prop. The phasing may change from lower load to higher loads at the same rpm.

Can you solve for what velocity the fuel would need to leave the injector to cover the distance from the injector to the intake valve for any given RPM? Maybe it really needs that much of a head start...? :roll:

I had a look to the bench you do use, on your company web pages.
What a nice Equipment !
What a pleasure it should be to work on such a bench !
We have a home made inertial bench, and it is not a good solution. But i suppose that yours costs a lot...

Nevertheess, i think in the same direction as you do: how many degrees does the engine turns before the fuel is "ready to use" ?
I mean, how many degrees of crank rotation are needed after the injection is finished to get the fuel:
- where it has to go (let's say to the intake valve)
- and also maybe to be completely evaporated (or not ?)
There are so many unknow variables : speed of fuel (combined with air speed, which can be >= 0, and not constatnt ), time used for evaporation (but does evaporation occurs really ?), ...
What is sure is that each ms needed for fuel transportation = 15° of crank rotation @ 2500rpm.
So if that fuel transport takes 6 ms, it is 90°, and i have to take it into acount when i try to figure out what is happening.

What i will do is repeat my AFR test at 2 different rpms (for instance 1500 and 4000), so i will have figures for 1500,2500 & 4000 rpm
And i wil also put the injector closer to the valve, and see what it changes.

Maybe will i have a better understanding of what happens with these datas.
On the other hand, maybe will i do it for nothing, as all these tests are done at idle, and what is really relevant for us is what happens at WOT ...

Anyway, i will keep you posted :)

Have a nice weekend,
Pierre
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Re: GX35 Honda 35cc 4stroke

Post by jsmcortina »

ol boy wrote:I would spray fuel just after TDC to catch the beginning of the intake stroke.
That's not the beginning of the intake stroke, it is the beginning of the power stroke.

James
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ol boy
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Re: GX35 Honda 35cc 4stroke

Post by ol boy »

jsmcortina wrote:
ol boy wrote:I would spray fuel just after TDC to catch the beginning of the intake stroke.
That's not the beginning of the intake stroke, it is the beginning of the power stroke.

James

When I was running a 2 cylinder 4 stroke (satio 57 )with only a single crank pickup I turned on the batch fire angle feature. I found that with a trigger angle of 50* and a phase % of 30 would spray every crank turn just after TDC. The saito had an intake runner of several inches combining both sides into a single point where a TBI was mounted. Catching the hightest velocity of the intake charge was needed to keep the fuel from puddeling everywhere.

James.. When can we see the next alpha code with the kick start stuff?
306 SBFord, Torquer II EFI intake, 60 lbs injectors, 8 LS2 coils, VS Racing 7668 turbo, 4R70W, MS3x fw1.4 w/built in trans controller.
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Re: GX35 Honda 35cc 4stroke

Post by jsmcortina »

ol boy wrote:James.. When can we see the next alpha code with the kick start stuff?
It isn't forgotten, but not coded yet.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
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New users, please read the "Forum Help Page".
PierreL
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Re: GX35 Honda 35cc 4stroke

Post by PierreL »

Hi Ryan,
Just to keep you informed: I finished my tests two weeks ago.
The only relevant things i found:
- Injection timing angle has a big impact on AFR at idle.
- But (very unfortunately in my case), i can not see a significant difference at WOT. To be complete, if there is a difference, i can not measure it because of the poor accuracy of the Tools that i use (LC1 lambda sensor + inertial bench)
So, i come to the same conclusions as a lot of others did before me : injection timing is effective at iddle, do not expect a lot of gains at WOT.
Nevertheless, it was an intersting part...
Regards,
Pierre
ol boy
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Re: GX35 Honda 35cc 4stroke

Post by ol boy »

What's your duty cycle at wot at max rpm?
306 SBFord, Torquer II EFI intake, 60 lbs injectors, 8 LS2 coils, VS Racing 7668 turbo, 4R70W, MS3x fw1.4 w/built in trans controller.
PierreL
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Re: GX35 Honda 35cc 4stroke

Post by PierreL »

ol boy wrote:What's your duty cycle at wot at max rpm?
I did not record the duty cycle (i never use it as my injector is over sized)
But pw= 4.662 ms @ WOT, 6000 t/min.
Based on the fact that 1 cycle = 20ms @ 6000 t/min, i assume that duty cycle should be 100x4.662/20 = 23,31 %

Do you see anything wrong ?

Thanks,
Pierre
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