Vespa gts 250 fuel tuning
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Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Fri Jun 21, 2019 7:17 am quote
Going to add a dobech ejk, looks like it will fit the bill since I don't want to up the redline, and the malossi is $100 more.

Thoughts?

Will update on tuning, just need to weld a o2 bung on.
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Mon Jul 29, 2019 7:26 pm quote
Unfortunately, my wideband controller wasn't working, but using a combo of acceleration runs and feel I was able to dial in some settings that improved the initial throttle dead spot and made the bike quicker.

The mods are the arrow exhaust and some airbox trimming with some uni push in filter hole inserts
Hooked
2008 GTS250, 2009 S150, 2017 GTS300Super, 2006 GT200
Joined: 18 Oct 2014
Posts: 206
Location: Houston
Sun Aug 11, 2019 5:43 pm quote
Are you saying you bought the Dobech controller but it didnít work? I went to their website after reading your post and it reads like itís a great product. Sucks it didnít work for you.
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Sun Aug 11, 2019 8:04 pm quote
rob g wrote:
Are you saying you bought the Dobech controller but it didnít work? I went to their website after reading your post and it reads like itís a great product. Sucks it didnít work for you.
Controller works great, I was talking about my standalone wideband controller. The power was way too noisy for the controller. Once I connected it to a separate battery it worked fine. I did a run where I pulled the ejk, and the stock map was afr of 15. With the ejk reinstalled, it's 13.4, which isn't great, but one can only do so much. Throttle response is better off idle and much less lean popping. This is with some UNI push in filters and a arrow exhaust
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Fri Aug 23, 2019 2:46 pm quote
I ended going up a size on the injector to the IWP158.

That brought AFR to ~12.5. and to the lower range of adjustment on the ejk.

So even if you just did the injector, it would still be a bit lean.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Tue Aug 27, 2019 5:05 pm quote
I just finished installing a PLX wideband lambda sensor & Forcemaster 2 on my 250. The PLX sensor came with a narrow-band output, that is supposed to satisfy the ECU, but I am getting a CEL a few seconds after starting. I suspect that I need to plug in the some/all of the remaining sensor wires (Right now I just have the PLX o2 output fed directly into the OEM lambda pigtail). I haven't ridden the bike yet, still trying to get the AFR to a point that I am comfortable with.

Here is a video of the gauge in action: https://youtu.be/lpKk48jFukA

Current motor spefications:
- Malossi V4 head (with mild polish, port matched intake & exhaust) cylinder & piston
- Malossi Forcemaster 2 on preset 3
- Polini camshaft
- PM-80 without baffle
- UNI filter on OEM intake tube
- OEM fuel injector



Sort of related: My motor has always sounded like the intake is "gasping" for air during warm up. I can now see that it runs pretty lean during this period also (around 17:1). Occasionally the motor will stall when it reaches operating temperature, but will start back up just fine and without the gasping sound. The video above is already at operating temperature, which is the only way I have been able to attempt to tune the AFR.

Does anyone know anything about this?

IMG_20190827_172636.jpg

Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Tue Aug 27, 2019 6:07 pm quote
17 afr is extremely lean especially at cold start where it should be richer than normal idle. I still have my narrow band as it is needed for closed loop.

With all that work I would bet a bigger injector is for sure needed. Just look at the sparkplug. It's probably white not medium brown.

Not sure how the narrow band output on your unit needs to be configured.

Idle should be in the 15/16 or so.
Wot should be 12.3-12.7
Cruise should be 14.5-15

There are charts online that show good AFR targets.

Another thing to consider is the cone filler, the runner length is tuned to resonate at the power band RPM. Going shorter means a higher resonant rpm. A little restriction helps sometimes
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Tue Aug 27, 2019 8:57 pm quote
raceratb wrote:
17 afr is extremely lean especially at cold start where it should be richer than normal idle. I still have my narrow band as it is needed for closed loop.

With all that work I would bet a bigger injector is for sure needed. Just look at the sparkplug. It's probably white not medium brown.

Not sure how the narrow band output on your unit needs to be configured.

Idle should be in the 15/16 or so.
Wot should be 12.3-12.7
Cruise should be 14.5-15

There are charts online that show good AFR targets.

Another thing to consider is the cone filler, the runner length is tuned to resonate at the power band RPM. Going shorter means a higher resonant rpm. A little restriction helps sometimes
That's what I think is odd, it has always made the gasping noise during warm-up, which I can now assume correlates with running lean. I suspect it might be programmed to do this to get the catalytic converter up to temperature. Right now "cold" start is roughly 100įF where I live, so I'm not sure if it really has to warm up for very long.

The cone filter is directly on the OEM runner. I was running a pod filter directly off the throttle body, but I decided to give this a try for better intake temperatures & correct runner length.

[/img]
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Tue Aug 27, 2019 9:34 pm quote
If you look at the MIU just to the right of the screw holding the fuel line, you see that cone shape in the casting. That's a idle air control valve. The wheezing your are hearing is likely that valve opening up to raise the idle to keep the bike from stalling. Op temp is ~180 so even though 100 is a good start, it's still going to put the ECM in it's warm up sequence. It was happening with the airbox, only you couldn't hear it.
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Tue Aug 27, 2019 9:41 pm quote
I'd suggest welding on another bung for your wideband, especially since there is a heater circuit on the narrow band you will need to emulate
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Fri Aug 30, 2019 4:45 pm quote
I temporarily wired up the OEM lambda sensor, with the PLX wideband controlling the 0-1V signal (black wire), and got the CEL to turn off. The ECU must do a check that involves the lambda ground (gray) and two heater wires (white).

I don't really want to install a second sensor bung in PM80 exhaust, and I also don't think that there is enough physical room for two sensors anyway. I'm going to look into lambda sensor simulators or a place to physically mount the OEM sensor in the engine bay. Most of the simulators I can find are for tricking the rear sensor (post-catalytic converter), which obviously is not present on this motor.

The lean AFR during warm-up is still present, and the CEL had nothing to do with it. I have also noticed that if I restart the motor with two bars (out of 11) on the temperature gauge, the warm-up cycle resumes as expected (without the noise, and with proper AFR).
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Fri Aug 30, 2019 4:56 pm quote
You are correct, the ECM will be looking for a open circuit (both sensor and heater). If you figure out the proper resistance, that will give you a wattage for the resistor. You for sure want the sensor input for the closed loop cycle. 2 bars likely puts you out of the cold cycle sequence, so no high idle.
Hooked
2008 GTS250, 2009 S150, 2017 GTS300Super, 2006 GT200
Joined: 18 Oct 2014
Posts: 206
Location: Houston
Fri Aug 30, 2019 7:52 pm quote
Where do yíall read to learn about this stuff? Extra bungs, widebands, narrow bands, what checks what and the things you do to trick it? Fascinating to me and I want to be able to participate in the conversation but I donít know shit.

I just picked up an 08 250 with the intent to mod it and it looks like to do it right Iím gonna have to do a lot more than just slap on a new 4v head and cylinder kit. Iím gonna need some electronics.
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Sat Aug 31, 2019 7:12 am quote
There are some books out there on fuel injection. But without a logging wideband sensor like the innovate LM series, any changes you make will just be a best guess. The AFR targets are somewhat generic which makes things easier. Direct tuning the MIU would be best, but that doesn't seem to be a easy option. There is some software for the MIU3 but mine is MIU1
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Tue Sep 03, 2019 1:34 pm quote
rob g wrote:
Where do yíall read to learn about this stuff? Extra bungs, widebands, narrow bands, what checks what and the things you do to trick it? Fascinating to me and I want to be able to participate in the conversation but I donít know shit.
Google mostly. These topics come up more frequently on other forums where the motors get modified. Most people interested in wideband sensors are also running boost, where the AFR is even more important since things can go wrong much faster.

I was lucky enough that my car (Honda S2000) came with a wideband lambda sensor from the factory, and that there were many options for e-tuning. This has helped me understand the terms/concepts and how they transfer to a Vespa.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Tue Sep 03, 2019 2:02 pm quote
raceratb wrote:
You are correct, the ECM will be looking for a open circuit (both sensor and heater). If you figure out the proper resistance, that will give you a wattage for the resistor. You for sure want the sensor input for the closed loop cycle. 2 bars likely puts you out of the cold cycle sequence, so no high idle.
I did measure the resistance of the lambda sensor out of curiosity, and it was around 11 ohms if I remember correctly.

I need to read-up on resistors, and see if I can come up with the correct way to wire this in.
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Mon Sep 16, 2019 4:42 pm quote
raceratb wrote:
https://www.amplifiedparts.com/tech-articles/resistor-power-rating

20w or greater
I purchased and temporarily wired a 10 ohm 20W resistor, and it seems to work! No more CEL at startup, the ECU is satisfied and thinks that there is a lambda sensor connected.

I still need to figure out a way to mount it permanently... I can see that the heat will probably be an issue. It seems to run cooler than the o2 sensor it was replacing, so I guess it's a win

Other than that the gasping noise at cold start is still present, and the AFR is pretty lean. A minute or two of idling and 1-2 restarts makes the noise go away and AFR right where expected. I'm starting to think that the amount of intake air at cold idle may be outside of what the OEM tune can handle. As soon as a little heat is generated, the parameters are within the table's window of operation.

Also for anyone wondering: the Malossi Force Master 2 appears to be fail-safe. You can unplug the ECU/diagnostic port connection only and the bike will still run.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Tue Sep 17, 2019 6:26 pm quote
Update: Heat is definitely an issue. I purchased some other 10 ohm 50W resistors with a built in heat-sink, and the resistor still gets up to about 225į F after a few minutes. It heats up way faster than the engine does.

So I tried a 20 ohm resistor (two 10 ohm resistors in series), and the temperature seems to be more manageable while still satisfying the ECU (the heat output is now 10W instead of 20W).

I will be adding other resistors as a test, in hopes of getting the heat output very low.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Wed Sep 18, 2019 4:47 pm quote
AnnDee4444 wrote:
Update: Heat is definitely an issue. I purchased some other 10 ohm 50W resistors with a built in heat-sink, and the resistor still gets up to about 225į F after a few minutes. It heats up way faster than the engine does.

So I tried a 20 ohm resistor (two 10 ohm resistors in series), and the temperature seems to be more manageable while still satisfying the ECU (the heat output is now 10W instead of 20W).

I will be adding other resistors as a test, in hopes of getting the heat output very low.
So 30 ohms seems to be the magic number. 40 ohms is too much resistance, and the ECU lights up the CEL.

Assuming 14.5V, the resistor would consume about 7W, which is 1/3 the wattage consumed with the 10 ohm resistor I started with.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Thu Oct 03, 2019 12:35 pm quote
Slight update: Even with a 100W resistor, the 7W of heat was still an issue. So I dove in deep and ordered a 500W 30 ohm "braking" resistor. It's definitely overkill, as I don't feel it heat up at all after 10 minutes of idling. I have it temporarily occupying the original charcoal canister location.


I do have a new issue though: The CEL light comes back on after about 5 minutes of idling. I suspect that the ECU does not like the 14.7 AFR at idle, and attempts to lean out the mixture until pegging the fuel trim. Has this happened to anyone else with the ForceMaster2? The CEL resets after restarting, and I haven't attempted to read the code yet (I'm not even sure it would be possible to read a code with the ForceMaster2 plugged in... I would need to parallel the diagnostic port K-like which is a serial connection...)
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Thu Oct 03, 2019 1:20 pm quote
You probably need to look at the codes, your gauge should emulate the narrowband response, but that resistor may be of just enough to throw a heater circuit performance error. Heating up will change the resistance.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Mon Oct 14, 2019 7:41 pm quote
Finally got around to doing a road-test.

It looks like the Malossi ForceMaster2 cannot adequately compensate for the modifications on my motor (Malossi V4 kit with mild port & polish, Polini cam, port-matched intake & exhaust manifolds, PM-80 w/o silencer, pod filter on OEM intake tube). With the ForceMaster on profile 3 and adjusted for maximum richness on the high speed dial, the AFR at WOT is a steady at 14.1:1. From what I have read, I should be aiming for something closer to 12:1.

I may try switching back to the MP3 400 fuel injector and using the ForceMaster to lean-out the AFR (at least at idle). Last time I rode with this injector I believe it was rich enough to fuel-wash the cylinder and break off the piston ring-lands... (FWIW: this was without the Polini cam)
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Mon Oct 14, 2019 8:52 pm quote
IWP158 injector 170cc/min
Worked for me. Lots of Weber style injectors
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Tue Oct 15, 2019 10:27 am quote
raceratb wrote:
IWP158 injector 170cc/min
Worked for me. Lots of Weber style injectors
I'm going to have to try the IWP158.

The MP3 400 injector I used was a IWP048 @ 215cc/min. (36% increase)

Do you know if the IWP143 will work? It's 184cc/min (16.5% increase)
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Tue Oct 15, 2019 10:35 am quote
Couldn't say specifically, but given your extensive mods, probably. Remember the only thing a piggy back tuner can do is modify WOT, otherwise the closed loop trims can adjust. For me, the 170 needed a little extra, but was within range of what the EJK could handle. If you overshoot, chances are the tuner can't go negative. For closed loop if you want richer, adjust the simulator output curve to slew slightly lean.
Ossessionato
'15 Blue GTS300 Super, '18 White GTS300 Super
Joined: 01 Nov 2005
Posts: 2590
Location: Sydney, Australia
Tue Oct 15, 2019 1:18 pm quote
The IWP158 I was using managed to get itself jammed open. So I have a couple of new ones in the mail now from Alibaba (Hegneyauto.com) in China. These have three holes, and I seem to recall my jammed one had four. Four would be better for fuel atomisation.

Lisa at Hegneyauto offered me a batch of them at a discount price, but I didn't have a use for 3000 of them.
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Tue Oct 15, 2019 1:38 pm quote
Amazon
New Fuel Injection for VW Pointer, Polo, Derby 1.8L 05-11 - IWP158 https://www.amazon.com/dp/B07CXBL2RC/ref=cm_sw_r_cp_apa_i_eXJPDb08Y840G
Ossessionato
'15 Blue GTS300 Super, '18 White GTS300 Super
Joined: 01 Nov 2005
Posts: 2590
Location: Sydney, Australia
Tue Oct 15, 2019 3:59 pm quote
raceratb wrote:
Amazon
New Fuel Injection for VW Pointer, Polo, Derby 1.8L 05-11 - IWP158 https://www.amazon.com/dp/B07CXBL2RC/ref=cm_sw_r_cp_apa_i_eXJPDb08Y840G
But they don't ship to Australia.
The injectors usually come in packs of 4 or 6 or 20, and are very difficult to find in singles. I ordered 4, one for each of my two GTSs, and a spare for each.
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Mon Oct 21, 2019 8:26 am quote
I bought my IWP158 from eBay for about $20.

Did some more testing... I'm not sure I like the ForceMaster solution. I can't seem to get a consistent idle AFR. It's always fighting against the fuel trim adjustment. With the IWP158 the only way to get a decent idle AFR is to use map setting 1 or 0, and lean out the low speed dial as much as possible. I was able to control the factory injector much better than this.

I spent a few hours this weekend researching Megasquirt, but eventually decided against it. From what I have read, the TPS is a digital signal. This could be solved with an external TPS sensor (they make kits for Carburetors). The other main issue I can see is the that I have no idea of how to control the IAC on the throttle body. There is a YouTube video of a Megasquirt conversion, but they are using an aftermarket throttle body and piggybacking onto the factory ECU.

I think it's time for me to look at tuning the ECU again.
Enthusiast
2008 GTS 250
Joined: 14 May 2019
Posts: 77
Location: Rancho Palos Verdes, CA
Mon Oct 21, 2019 8:56 am quote
If you are going the megasquirt route, check out the microsquirt. Assemblied and sealed. Also, with all the EFI dirt bikes, throttle bodies are ready to come by used
Hooked
GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Mon Oct 21, 2019 9:17 am quote
That's exactly what I was looking at.

I just ordered another Kess/Ksuite from a different supplier, so with any luck it will be able to read the ECU...
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