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Hi all,

 

After some consideration about DRZ400SM carb choices (Pumper vs CV) I decided to that I would like to give fuel injection a go.  This has been a project that I have had in mind for a few years thinking that I would be a great way to get the best out of a bike.  At the time of inception I didn’t know that it was going to be a DRZ400SM.  I did know that I was going to uses a Microsquirt to do the injecting.  I have done a couple or car FI conversions – a 77 V12 Daimler Double SIX and a Mitsubishi RVR (4AG63) – Both started out life as FI vehicles making them easy to convert to aftermarket – tuneable ECU’s. Both running MegaSquirt 2’s with outstanding results.

Moving along – when I brought the bike I was a little underwhelmed with the performance off the showroom floor.  I got a Yoshimura rs2 for a good price 2nd hand – cleaned it up and rejected the SM’s standard CV carb did the 3x3 mod and that was much better. Then I had a ride on an E – pumper carb -super snappy, so I started to have a look around for one to put on the bike.  I was a bit overwhelmed with the price of said carbs new.  I got to thinking about fuel injection and how good that would be, as well as fully programable ignition and the room for mechanical mods further down the track. It was an idea I couldn’t leave alone.

So here we are – the bike is just back together and operational.  It is still in need of some tuning but preliminary results are it is a success. It is much more “Stompy” than the CV carb’ed version and at the onset looks to be more fuel efficient. 

The throttle body come from an injected LTZ400 which is a very close relation in terms of motor to the DRZ.  It is made by Keihin and 38mm.  It has the same external diameter of the Keihin MX39 carb that it commonly fitted so the boot you buy for that carb conversion also works for the Throttle Body conversion.  I made a bell mouth adaptor for the air box side to fit the standard SM air box boot.  The throttle body has an integrated MAP and TPS sensors now used by the Microsquirt. Careful bench testing of the sensors enabled a calibration table to be made for each to enable the Microsquirt to read the sensors accurately.  I’m not sure of the purpose but the LTZ had an axillary air plunger on a cable system (hot start / cold start?).  I found Keihin spares had a choke plunger that fitted with no cable involved – so I now have an auxiliary air knob for fast idle situations.

 I also brought the LTZ flywheel with the view of fitting it to gain the required triggering for the ECU.  The flywheel is subtlety different in too many ways to fit the DRZ, for one it is 1.5mm larger in diameter and has about 200grams more mass and the stator for the injected LTZ is also of bigger diameter.  I liked the 18-1 tooth triggering arrangement though.  So I had the existing flywheel modified, taken down by a couple of mm  - removing the standard trigger teeth for the CDI unit and a ring made with the 18 – 1 triggers machined into it, and had that slipped on.

I had considered the LTZ fuel system as they have an out of tank pump, but after a good look I decided that there was no room for the swirl tank / pump combo.  Other considerations were the extra plumbing required for fuel, low pressure fuel, return fuel and high pressure fuel also the pressure regulator and fittings.  I had a good hunt around and found a fuel pump with integrated regulator, this also helps keep the plumbing to a minimum as the fuel connections to the regulator are integrated in the pump.  I designed printed some mounts to hang it in the space where the carb float bowel would normally be.

There were a few minor hiccups along the way – the high pressure fuel barb aimed directly at the frame spar, this was rotated on its O-ring with the use of a bracket to become parallel to the frame.  The cover for the throttle body interfered with the oil breather box.  I split the oil box in two and designed and printed a new side with a scallop in to clear the throttle cover.

I’m a firm believer in the right tools for the job too so I have fitted an innovate wideband O2 meter, while the end game is not to use the O2 for day to day use (i.e. have the bike tuned well) I need such a device to complete the initial tuning. The control box for the O2 sits in on the frame just forward of the tank rubber, in the place that the CDI coil used to sit, the O2 Probe can be seen on the side of the exhaust.  The control box is connected directly to the ECU to provide feedback on mixture richness ETC.

The CDI coil has been replaced with a Nissan S15 Coil on cap item.  This has an integrated igniter that can be triggered directly from the Microsquirt.  It needed a small amount of modification to fit, I had to cut about 10mm from the bottom of the plug cap so the conductor would reach the bikes spark plug.  I also printed a spacer / dust cap for the top to make the system as waterproof as possible.    

The electrical system I tried to keep simple.  One extra relay for fuel pump, injector and spark power and two fuses, one for fuel pump / injector and one for spark. The relay is mounted between the shock body and the back of the air box, the fuses are above it.  I selected waterproof items where possible as I do have an 18/21inch wheel combo for off road / adventure riding.

 

Cheers

John

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Hi,

 

The tuning is still a bit ragged around the edges - lots of spots where its too rich - that's a tuning thing.  But other than that wickedly stompy, super crisp throttle response, seat of the pants says more powerful than the CV carb.  Its been complete now for about a day, so I'd say we're in the tuning / shakedown phase.  I tuned the cold start and warm start this morning so it just bursts into life with a press of the button.  I spent about an hour last night around idle getting timing sorted for steady idle. Ill keep you posted.

Cheers

 

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That's awesome. I'm actually surprised Suzuki isn't delivering the bike from the factory with those mods yet.

 

How does it compare to your buddies E? Generally speaking, throttle bodies are larger than the carbs they replaced. For example my 250F uses a 44mm. 450's use between 43-48mm. The factory Z400 TB is actually only 36. Just some food for thought as you go forward. You have definitely contracted DRZ moditis for which there is no cure.

 

 

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3 minutes ago, ohiodrz400sm said:

That's awesome. I'm actually surprised Suzuki isn't delivering the bike from the factory with those mods yet.

 

How does it compare to your buddies E? Generally speaking, throttle bodies are larger than the carbs they replaced. For example my 250F uses a 44mm. 450's use between 43-48mm. The factory Z400 TB is actually only 36. Just some food for thought as you go forward. You have definitely contracted DRZ moditis for which there is no cure.

 

 

Ok, Its a bit hard to say how it compares at the moment. I need a week or so to get it tuned and shaken down.  In my mind  - at the moment I'd say its a little bit crisper on the throttle than the E.  I'll get the SM tuned up and then enlist my buddy to do some back to back trialing.  It's not out of my mind to do some dyno tuning as well - it all takes time.  I didn't really look much further than the LTZ for the throttle body.  Mr Suzuki knows his stuff, there will be something in the choosing of the size - mid range response, intake air velocity are just a few.  Its a road bike that won't see full open throttle much so peak HP was a little down the list.  I was surprised, on my many visits to the local bike wrecker, to find that some bikes of orange persuasion use Keihin supplied throttle bodies. From what I have seen a few of these in larger sizes might be a good fit - if your after more HP.  There was certainly choice amongst the orange bits   

 

Cheers

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Mr Suzuki knows his stuff, there will be something in the choosing of the size - mid range response, intake air velocity are just a few.    


Well that and the stone stock LTR-450 only laying down 42 hp was another consideration. Of course a Cherry Bomb boosted it significantly but it's bad business if your little "Sport" quad is nearly as powerful off the showroom floor as your "Quad Racer"

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Great work mate. would like to see the Dyno results if you go down that path.

 

 

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Nice. This is something I've been wanting to do for a while now, but just haven't found motivation. Glad to see someone else doing this!

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2 hours ago, ohiodrz400sm said:

Can you post your Bill of Material with all part numbers ?

 

Correct my math if I'm wrong but you're at $1251 USD so far?

 

 

Yeah, it was never about the money - also consider it not only a carb replacement but also a CDI upgrade.   I will post a parts list / spreadsheet at some point and a Microsquirt Tune file (That's the time taker) - after I get everything collated and after the shake down.

 

Cheers

John

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Throttle bodies are the cheap part of these kits so changing to a bigger one wouldn't be hard once up and running . I have an older CFR250 tb(42mm) and a  newerCRF250(?) tb here (44mm smallest end to 52 or 54mm at the butterfly), and a WR250(36mm) for my owm Microsquirt setup(not my drz), but decided to go with dual tb off a '13 Ninja 300 instead due to that motor being setup with dual carbs already . Kawasaki has some neat setups , dual injectors , one being back in the airboot inlet before the tb that precharges the air stream for good throttle response and acts as a longer intake tract for lowend, interesting system. All that wiring and finding room for it plus the fuel pump & plumbing has had me dragging my feet in hooking it up not to mention riping a good motor apart just to install a trigger wheel .Be interested in just which sensors used . 

My TE510 has a "choke " knob on it as well (Keihin tb) as well as my LTR450 only it has the lever on the handlebar , they're open efi systems so they can't automatically add fuel on cold startup, but with the Microsquirt a person can make it a closed loop I believe .

 

.

Edited by jjktmrider
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30 minutes ago, jjktmrider said:

Throttle bodies are the cheap part of these kits so changing to a bigger one wouldn't be hard once up and running . I have an older CFR250 tb(42mm) and a  newerCRF250(?) tb here (44mm smallest end to 52 or 54mm at the butterfly), and a WR250(36mm) for my owm Microsquirt setup(not my drz), but decided to go with dual tb off a '13 Ninja 300 instead due to that motor being setup with dual carbs already . Kawasaki has some neat setups , dual injectors , one being back in the airboot inlet before the tb that precharges the air stream for good throttle response and acts as a longer intake tract for lowend, interesting system. All that wiring and finding room for it plus the fuel pump & plumbing has had me dragging my feet in hooking it up not to mention riping a good motor apart just to install a trigger wheel .Be interested in just which sensors used . 

My TE510 has a "choke " knob on it as well (Keihin tb) as well as my LTR450 only it has the lever on the handlebar , they're open efi systems so they can't automatically add fuel on cold startup, but with the Microsquirt a person can make it a closed loop I believe .

 

.

The object of the exercise was to look stock Suzuki,  Yes you are right the TB can easily (some adaptors etc) be swapped out at a later stage.  I have done a bare install so its sensors only - there is no idle air manipulation except the manual knob, that lets you add some more air to the bypass loop hence increases the engine idle speed - to overcome cold thick oil.  The MS compensates for the cold engine with some warm up enrichment that is set up in a table (dependant on coolant temperature).  Fortunately where I installed the MS is about 6 inches from the throttle body so the wiring loom was not too bad .I made the loom custom as not to have any excess wiring in loom so I only populated what I needed plus a few extra - for table switching - these are tapped safely away.  Some time was spent figuring out where the fuel pump would sit and how the plumbing would work.  As for the trigger wheel - I had a spare flywheel modified and tested it for triggering before getting it installed.  The sensor list is :  Air intake temp, Throttle position sensor, Coolant sensor, manifold pressure sensor.  The reluctor for triggering is the standard Suzuki fitment on the DRZ.  

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Sweet job and huge respect for the know-how and work involved  :worthy:  Who knows, if the KLX250S can switch to FI, maybe Suzuki would do the same eventually?  Very cool that you did it yourself in any case.

Completely unrelated side question: which shifter is that and did you have to bend it?  It looks like it's sitting nice and far away from the case saver.

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