zetec 1.8 GSXR throttle bodies

[stevefly]

I am trying to get my Zetec 1.8 running smoothly on gsxr TBs and megasquirt 2 ecu, does anyone have a successful map for this set up? I bought the car hoping I could resolve the lumpy  issues when pulling away ,running rich at low revs and lean when pushing hard ect but I am failing to get to grips with Tuner studio and the whole mapping thing! it would be great if I could burn a successful map to my ecu compare it to my current set up and then try to refine it!

or if that fails could recommend an expert in the north!

cheers steve

[Kingster]

Take it to JDM Dyno in Kirkbride. Not too far from you and Jonathon really knows what he’s doing. 

[Thrustyjust]

As Chris says, get it on the rollers. You could spend a fortune mucking around and causing damage from bore wash if running rich etc.

[SootySport]

Did you balance the carbs and have them re-jetted, you need to do that first.  Also fuel pump pressure needs to be correct.

[Kingster]

5 minutes ago, SootySport said:

Did you balance the carbs and have them re-jetted, you need to do that first.  Also fuel pump pressure needs to be correct.

There’s no carbs to balance or jets to rejet 

[SootySport]

Just now, Chris King - Webmaster and Joint North East AO said:

There’s no jets to rejet 

Ah, is that so, didn't know that, how the hell do they work then?    My Yamaha R1 carbs needed re-jetting.

[SootySport]

Just realised they are throttlebodies

[Kingster]

13 minutes ago, SootySport said:

Just realised they are throttlebodies

[stevefly]

Its  been to Jonathan at JDM 144  bhp @ 5900 good flat torque right through the revs,He says its a good engine just has this problem pulling away,I have read that the TBs may be too big and I should downsize to GSXR600  also it is set up to only use the main (primary )injector.

Anyway I am going to try the 600TBs The other option was to put in vernier pulleys and hot cams as apparently once above 175bhp the TBs are better suited to the fuel air mix provided. it certainly seems like I will have to suck it and see.4

[corsechris]

Before swapping to the 600 size (although TBH, that's probably a better match to your engine anyway)....bear with me and wade through the following:

Fitted GSXR600 TBs to the XFlow many moons ago - brilliant, no issues, no problems.

Roll on a few years and fitted a stock 2l Zetec, swapped over the TBs. Started with a base map, not too bad but took it for mapping to get the best out of it and hopefully solve the slight flat spot just as throttle was cracked open and some wicked backfiring at times. Long story short....those TBs are incredibly sensitive to the initial few degrees of movement and to cure the problem needed an ECU that allowed user-control of the load site spacing/resolution. The ECU on the car was too old to offer that feature but a quick ECU swap to a newer model proved the point.

So, to the point...does your ECU allow you to set the first few load sites to be VERY close together? If it does, great, close them up for the first say 20 degrees of throttle opening so that each load site os only one or two percent from the last one. This gives really fine control over a small area. You will sacrifice a bit of fine control higher up, but generally, that isn't an issue as the relative change in airflow per degree of throttle movement drops off really quickly as you open it up. Basically, you get a massive change in airflow for a tiny change in throttle angle at the very bottom and unless the ECU properly monitors this, you will get a lean spot.

On our car, the symptoms were awkward to pull away smoothly on light throttle and some pretty shocking pops & bangs as you transition on & off throttle when cruising.

The reason it didn't happen with the Flow was that it had the usual big valves, big cam setup so made very little vacuum at low revs so the sensitivity issue never came up. The stock Zetec sucks like crazy so aggravated the problem.

If you are thinking of some lumpy cams, you may well find that sorts it anyway as you might not hit the problem area any more.

 

Good luck.

[Kingster]

Another point to note with bike throttle bodies is how they are spaced. 

Mine were problematic at very initial throttle openings until I “beefed up” the home made spacers in between each throttle body. 

Basically, the way GSXR bodies work is the first butterfly opens the second and the second opens the third etc. So any flex in the linkage means that the first butterfly can open before the last one moves the TPS. 

So you get one pot very lean before the ECU is told by the TPS to chuck fuel in. 

So check the inter butterfly connections. 

[corsechris]

12 hours ago, Chris King - Webmaster and Joint North East AO said:

Another point to note with bike throttle bodies is how they are spaced. 

Mine were problematic at very initial throttle openings until I “beefed up” the home made spacers in between each throttle body. 

Basically, the way GSXR bodies work is the first butterfly opens the second and the second opens the third etc. So any flex in the linkage means that the first butterfly can open before the last one moves the TPS. 

So you get one pot very lean before the ECU is told by the TPS to chuck fuel in. 

So check the inter butterfly connections. 

Good point. That was the first suspicion on my setup once we found it was going lean. Turned out I'd done a decent job of spacing and extending the inter-TB linkages as there was zero movement end to end. Second suspect was a dodgy throttle pot. That was fine too.

[stevefly]

great information guys even more to think about ,can you describe what i am looking for in the  inter butterfly connections. 

and Chris could you describe how you made the beefed up spacers between the throttle bodies?

cheers Steve 

 

[Kingster]

here’s mine. See the small alloy plates pop riveted to the butterfly actuator arms. They can flex and give you grief at low throttle openings especially as the vacuum is so high at that point. 

[corsechris]

I did basically the same thing as CK, but used steel angle of the same thickness as the existing parts on the TBs, fixed them on two faces to the original levers and spot-welded 'doublers' on so that the 'between body' adjusters had a lot more tension in the springs. Idea being to help prevent them from moving. Depending on your inlet manifold setup you can end up with a big space between the two middle ones - I did, but it didn't hurt despite losing dead dodgy. I did it that way as I was replicating the layout of a pair of DCOE 40s and wanted a simple bolt-on replacement. I grafted the TBs into the cut-down remains of a pair of dead DHLA 40s. You can just make out the outer flanges in one of the pictures. Not shown are the inner flanges that bolt to the manifold. It was a proper PITA to do it that way....

The attached pictures are the best I have I'm afraid. I first used these on the XFlow, back in 2005, as I mentioned, then transferred them over to the Zetec in 2006.

Having gone from zero issues with them on the Flow to some pretty impressive pops and bangs and a flat-spot on the Zetec, I confess my first thought wasn't to blame the TBs. You may well find that going from stock cams to some lumpy ones could solve the issue. I put a taller diff in at some point along the way and that had a minor beneficial impact on it as well, as it slightly shifted throttle position for typical scenarios where it used to pop more. Unexpected but not unwelcome. Just saying, it's surprising how one thing can impact another.

 

ETA. Looking at that picture now, I'm not sure I'd do it myself, but if you had real issues you might perhaps contemplate removing one or two of the return springs toward the throttle pot end of the chain to reduce the strain a bit.

Also, it reminds me that I fitted an IACV - you can just make out the small tubes at the bottom that go to the vacuum ports on each TB.

 

HTH