3T/2TG Hybrid AFR Troubles

[Celica_73]

Hi all

Ok it's been a year since the FINAL engine rebuild and I thank you for all your support but still not happy with the engine!

I'm not game to take it to the Chassis Dyno dude here after blowing the last engine up (although may not have been his fault) but he also didn't seem to know his way around Solex Carbies.

So the Problem is the engine never ran that great after receiving it from Goodmans (who rebuild and engine dynoed last build) has a flat spot when the accelerator pump. They were unable to test the pump out on their dyno before giving me the engine due to their setup.

Carby setup received was M 135 MA 160 P60 as purchased off you last year although i believe the MA has been drilled out to 170 not 100% sure.

Unhappy I've build a Sniffer pipe and using Techedge 2J1 kit to log and message the AFR to discover cruising and WOT was running at 12.5 idle was 15.5 (cams i think should make it read leaner then that)

I still have the old jets which were M 165 MA 200 P 55 i first tried the MA at 200 leaving the rest of setup as is and took it for another run. cruse was still 12.5 but WOT was now 13.5 result change as expected. Then changed P to 55 and left MA as 200 but cruising lean out to 16 so quick placed the 60 back then discovered the idle screw were 4.5 turn screwed out so i turned then in until i got a max idle speed and then .5 turn richer making it about 2.5 turn now. The AFR at idle is now 17.5 but cruise is 13. So first question does these sound reasonable result for the changes made and safe reading?

Now the flat spot is still there but better after making these changes. On heavy acceleration ie pumps in use the AFR goes off the scale at 8.25. Pumps were on mid hole setting so adjusted to lowest hole on the shaft (sure this is less accel pump). The spike was less but flat spot was still there.

I'm sure it's not a miss as it clears itself and the AFR climbs back to 13 over time with no change on the pedal.

Our last change was to disconnect the accel pump and try that. The flat appears to have disappear. The AFR still dips but only to 10 and climbs and the there doesn't appear to be only lean out with the pump disconnected. Not sure in the Pumps are still having some influence as we only removed the split pin and washes.

Could you possible share your thoughts on what to do, have any of you every had to disconnect accel pump before or heard of it?
I just don't want to blow the engine up again but i want reasonable power too with no flat spots.

Cheers Jason

[shelldrake]

I had this exact same issue, with my old hybrid and solexes. The solve for me was to buy some 45mm webers though. Plenty of people know how to tune them properly and I got a significant power gain.

So, to clarify, the flat spot is at wide open throttle (Full load)? Could you redrill the pump arm lower to make it squirt less fuel?

[Celica_73]

Yeah Just can't justify forking out around $1200 for another set of carbies.

OK to clarify when the flat spot raises it's ugly head here are some examples. Cruising at 100km in 5 gear at about 3000 rpm purring along very little throttle required. you then plant your foot to over take bang flat spot straight up then slowly clears itself and rpm shoot up.
Same thing occurs if you try to accelerate too fast from the lights or a stop. Which is kinda dangerous as most of the time i hit the flat spot is when i need to go in a hurry. General driving i don't even see the flat spot, only when you want the little more power.

I do have data logs for a couple of drives from the Techedge kit if you can open them.

[Turdinator]

Yeah Just can't justify forking out around $1200 for another set of carbies.

Doesn't have to be that much. See HERE. I used to have these carbies on my hybrid and made the 88rwkw with them. They have big chokes (36mm) for top end but being 40 DCOEs are more responsive than 45s at low rpm. Tunning should only cost another $200 - $300. So thats only about half what your talking about and it will drive like a dream...

[Celica_73]

Ok I have been in discussion with Rodger and started the conversation with basically the first post on this thread. So I've decide just to show the information here so other may use the info.

Turdinator: sure the carby's are only $400 but then I'll need the linkages plus the jets and venture to suit my engine on top of the labour of the person tuning the carbies $300.

Rodger: As for my current jets size I'll have a look when I get home. and let you know

Hi Jason.

I suppose I can copy all this across. There is good info in here and I did read the thread. Shall I or can you?

It is possible to change the pump jet. It is an independant jet accessed by removing the small round slotted Plug back from the Idle mixture screw, the plug has an O ring to seal it and there is one per barrel. Part #69 on the Mikuni diagram.

http://www.rmcarburetors.net/Mikuni%...ms%20table.htm

http://www.rmcarburetors.net/Tuning%20Tips.htm

They range in size by 0.5mm from 30 up to 60. The smaller the size the leaner the shot. The duration is as you know set by the pump stroke. I can supply any size for the Solex.

Regards

Rodger

Hi Rodger

I've started a thread up in the tech if you wish to post there so other may see. http://www.toymods.net/forums/showthread.php?t=46590

Yes the does flutter off a standing start only when you need the extra power to get going in a hurry Normal/Light driving no flutter.

OK so let me see your saying that maybe my nozzles a dribbling not spraying. Well when i rebuild the engine i also replaced all the carbies gaskets. and i test the nozzle to see if the meet the specs in the tractor manual. the spray duration was little shorter but the spray was more of a stream then a spray. Is there anyway of changing this? I not sure if you missed it but the accelerator pumps are currently disconnected ie spilt pin and washer removed and the mixture still dropped to 10.
Is it possible to Reduce to pump jet in these carbies? I thought the pump jet was in the casting.
I'm almost positive the pump are to blame if your foot is down a bit already not flat spot to WOT

Next the ignition mapping was setup on the dyno and is electronically controlled. 12 degrees static and 35 at 5000
straight line between the too. No vac advance although was looking into placing a MAP sensor into the controller for this. MAP sensor is connected and was also data log with the AFR next RPM .

Ok outer venturi size in 30

OK the AFR at idle i believe to be fine the lean reading is for 2 reasons: 1 the sniffer pip is unable to gain accurate reading below 2000 rpm, 2 the overlap in the cams. If the cruising mixtures are fine I'm happy to leave the Pilots as they are.

Cheers for all the info and knowledge everyone tells be to swap to Webber sure they are easier to get parts for and to fine people to tune them but I'm loving the sound of the Solex at WOT just hope i can sort this out.

Jason

Hi Jason.

I love this. Fantastic work. Now I have some good reference material

First up I see no real dangers present in what you see in the mixtures. Just a pain in the arse. Even the extreme lean readings. Of course if it where to run like that for all time then it will be detrimental. You are watching and not letting it go on too long, which is good.

Check the fuel map on the couple of my motors on the xT dyno thread.

Even with your engine specs it should be drivable and cruise ok but one issue leads into the next as you go through the transitions.

As a starter, do you know what timing and advance curve you have? Mine is currently 10 static and I use the 12 degree slot in the dizzy mechanical advance. For 34 degrees total mechanical and no vacuum and on ULP.


Now.
If the engine hesitates and flutters around when moving off from the lights or an intersection then it is dangerous and we need to fix this. Most times it is caused by mal-functioning pump circuits, some or all not working correctly. If they are dribbling out it can cause the next issue you discribe, but this would be noticable off the line and this is where to look first.

The flat spot on sharp acceleration and from what you have discovered is present from a too rich shot of fuel over a too short time and could be the fact they are not a clean shot caused by above. If all is ok then it probably needs a longer leaner shot. So a smaller size of pump jet and back to the same stroke length.

Of course this response only happens in the first 20% of throttle movement so if a broard flat spot is present during a full throttle run from low revs, once over any initial hessitation, is now caused by air speed. Here the cams and venturi come into play. We could also explore the choice of bleed pipe as this has an effect on the transition point from pilot to mains. We can experiment with a couple of styles to see if we can match the cams and venturi.

Can you recall what size outer venturi you have?

If it is siting at 13 and the idle is 17.5 it may well be worth trying one more size up Pilot. A #62.5. It will mean you can come back a bit on the idle mixture screw but may then be a bit rich at cruise.

Regards

Rodger

[Celica_73]

Rodger
The pump nozzle size is 45 not it's what about mid size. How small do you go but?

Jason

[Celica_73]

What sizes are available for the starter/choke jet as the Choke mixture seems a too little rich as well. Only notice since I've back the pumps and the idle screw down it now requires choke to start the engine.

Cheers

[Rodger]

The Type T Solex (on 18R-Gs) have #35 Pump Jet and I just confirmed we can use them in the S4/S5. I suggest trying a set of #35s and I can send four used ones as a trial.

The Choke jet can be changed as it has the same thread as the Main Air Jet but is a small OD used in the PHH44. Therefore they can be anything from #90 -- #250+ in steps of 10. OEM is #180. However once you get pump jets running again you will find you are not needing to use the choke. The reason it is hard to start without pump jets is, there is no way of getting a couple of shots of raw fuel into the intakes at start up.

Regards

Rodger

[Celica_73]

Another quick question for you Rodger or Carby gurus

The large venture what give you the indication that they are either too small or too large? Reason been as stated I'm running 30 but looking around most people here with the Hybrid engine are running 32 or 34. Also what do the different bleed pipe have affects with?

Cheer for all the information been mighty helpful. As for the starter jet I'll check when i get home to what the current size is. And might get a couple sizes smaller as it blows black smoke will on choke hence too rich. If you don't mind I'll get you to send them with the Nozzles.

Thanks again
Jason

[celicaspud]

Dude just go EFI and be done with it if you hunt around and be smart you will just about pick up everything you need for under $1500 the thing will run nice use less fuel and have more gravey and the dude that dynoed your car is a knob how the hell do you lean out a carby fed car long enough to kill it ok every one who has used a dyno has killed the odd rota but a carby fed piston engine get me some off the drugs he was on

[Celica_73]

celicaspud
Sure i could go EFI but i can't see how a well tune carby engine would produce much less more then a EFI. Plus the hassle of EFI fuel pump redoing the fuel lines getting a computer + installing the wire harness in the car. I'm also sure you would have to agree that an EFI system just doesn't have the same induction noise as Side draught Carbies at fulll song. I've nearly sorted the tuning out then It'll fine nothing to worry about. But i can see your point but just not interesting in going in that direction.

Oh yeah in the dyno dude's defence he probably does know EFI systems backward to front the fact he didn't have a clue about Solex is the main reason for no return. The engine died on the dyno but due to machining and not doing the proper calculation about the engine CR ended up being 13:1 that's what destroyed the engine.

Rodger
The Starter Jet is 180 think may try 150 if you could send a set and the pump nozzle would be much appreciated. Let me know how much I owe you and I'll transfer the money Think I still have your details from last time

Cheers Jason

[Turdinator]

Another quick question for you Rodger or Carby gurus

The large venture what give you the indication that they are either too small or too large? Reason been as stated I'm running 30 but looking around most people here with the Hybrid engine are running 32 or 34. Also what do the different bleed pipe have affects with?
...
Thanks again
Jason

Outer venturi depends on a lot of things. I would have thought 30 was to small for a hybrid, let alone one thats modified. What cam specs are you running?

[Rodger]

Jason,

I find your address from previous and send what I can. Four used #35 pumps and if I have a #150 Jet that will suit. No cost, consider it as support and what not used I'll get back.

#30 could be upped to a #32 or #34. The #30 gives you good low/mid range air speed. The 18R-G had #32 and the #30 is a good size for a stock to mild 2T/2T-G.
A small Venturi will show up as a power drop off at the top end as the carbs run out of air flow capacity. Normally Toyota sets the venturi and jetting to match the cam spec, hence everthing "runs out of puff" at the same time.

If the motor has good torque, as it should, then the #34 can be used to get the better out of bigger cams. I'll see what I have for the Solexes. Comes back to how you want to use the engine.

Regards

Rodger

Regards

Rodger

[Celica_73]

OK thanks Rodger

OK the engine on the Dyno lost power very quickly but it was at 6500 RPM the torque max out at 5000 but in saying that this is and daily driven car not looking for huge numbers at the top end looking more for a flat torque curve the peaky power. Goodman did say the engine was very fiddly to tune and had problems getting it to rev at the start, wonder if this could be to do with the Venturies.

I'll try to post the Dyno Chart for you to have a look at

Thanks
Jason

[Turdinator]

BP8ES plugs are quite cold. I'll be interested to see if they foul. Also with 293 degree cams it should definately rev. Shelldrake used to similar cams and from memory he liked the 34mm outer venturis best. Still drove well but freed up more topend than the 32mm.