Turbo carb tuning

Wheel House Motorsports · Oct 20, 2009

Alright, so i Got the rx1 motor running in my sled right now with just the primary on it, as its not quite ready to be snow/grass dragged to do any final testing.

I have the carbs all boost referenced the way there supposed to be, my fuel reference is off the nipples onthe carb boots all tied together, when i hammer on the thing and it builds boost, approx 8-9k the thing lean pops really bad and my afr gauge goes --- red.... its SUPER lean, First thoughts were that it is jetted way lean, then i thought for it to be gettng that bad, and only under boost would that suggest that my boost lines that T together for fuel pressure might have a leak in them, i need to go take a picture and check my boost vs fuel pressure as they both jump up, to make sure there increasing properly.

also, the spring thats in the fuel pressure regulator is a slightly different one that came in it, guy before me played with it and Im thinkin its stiffer, but that should not affect anything but my opening pressure base pressure yes? then the boost does the rising. just all thoughts on it.. gonna go check some stuff. i have all 4 of the nipples in a big T- situation and am wondering if that is leaking some and causing it to lean out, as my wastegate is set at 10psi and im only seeing 8 on my boost gauge which is t'd into the fuel system setup...

heinracing · Oct 20, 2009

how much fuel pressure are you running at idle?

brycter · Oct 20, 2009

we do need to know you fuel pressure base and what it rises to. also i don't like to tee any of the reference lines if i dont have to. Are you adding fuel to the carbs through a power jet? how are these being fueled? through the float bowls or a n20 switch? Is your fuel pump keeping up?
there is alot more questions but these are some of them.

Wheel House Motorsports · Oct 20, 2009

I have done a lot of reading so im not a total fool, my idle PSI is set right abouts 4-5psi, it kinda flutters a tad. I dont know exactly what my final psi number was as its hard to watch the tach, boost, fuel and afr all at the same time, but i am going to try and have my GF take a picture when i hit peak boost off all my gauges so i can check. the reason I have all the lines T's was that I wanted the carb signal to be balanced cuz im referencing from carb boots, that way it its actual motor, not whats in the aribox or whatever. I t'd em so its not gonna bounce really bad at idle when its vaccum pulsing.

I have a mallory 1:1 regulator, and a pump that can keep a large v8 moving, so thats not an issue.

the carbs are boost referenced all around, its an RX1 carb setup and from what i read you dont need auxilary fuel, just reference the float bowls and the carb caps.

I went out and did some more testing this afternoon before messing with anything, my wastegate is set to 10psi, and my boost gauge was hammering to 8 really fast, so i know im building the boost, but i think i had a small leak going to my boost gauge and so my fuel pressure regulatoras well, that would cause it to lean out at boost increased. When i got WOT from idle the air fuel goes from around 15:1 to high 12's to low 13's until the thing hits around 5/6# of boost then builds up to 8psi on the gauge, but right around 5psi the afr plummets to past 18:1 FAST... must be the point where boost starts to leak.

would i be better off referencing the vaccum/boost off a single carb boot? and BOV off one and boost gauge off another? just curious how to set it up to get the most accurate and functional reading.

I have moved my gauge line to the niple that feeds the wastegate, so eliminated a T in the system, but the fuel pressure gauge had 5 t's and is now down to four, so even if they leak ever so little, 5 of them would cause a large signal loss.... it runs really well under heavy vaccum, so seems like a boost leak in the t's to me... any ideas are greatly appreciated

POLARIS600cc · Oct 21, 2009

How are you loading the motor to build boost with only the primary clutch installed?

Wheel House Motorsports · Oct 21, 2009

POLARIS600cc said:
How are you loading the motor to build boost with only the primary clutch installed?

hamer on the throttle and a well designed turbo system! thats what i thought when i was seeing boost, but she spools FAST!

not ideal conditions, but its running weird enough I dont want to drag it into the hills for some road riding if its gonna be totally F'd, It got some more time today to single out problems, and see if its just a boost leak or im totally retarted.

brycter · Oct 21, 2009

you are going to have to trouble shoot each item with a vaccume guage? make sure that your diaphram in the reg is not wrinkled or leaking. test your tee set up with the guage. make sure that you don't have any kinked reference lines.

One other thing is fuel regulators do not like vaccume all they want is boost signal so you might want to change the regulator signal line to the charge tube or air box. I if am picturing this right you are grabbing you signal after your carbs? You still might be pulling a little vaccume at boost level.

Just some thoughts. pics also help us see what you got going on.

just my .02 call me if you would like maybe i can help hash it out.

bryce
801-807-8046

heinracing · Oct 21, 2009

what is the pressure your pump can run?

i ordered a 40psi pump one time got it installed it had a issue figured out store sent me a 8psi pump so at 10lbs of boost was only getting 8 psi of fuel so lean burn down

just checking also i would put the reference line into the airbox or charge tube

Wheel House Motorsports · Oct 21, 2009

alright, I will try swapping my reference over to the charbe tube... i want to say i was told in the t-yami section that it was supposed to be post carb, but ill check, that could be causing me some issues. and i know the pump is a gooder, i have run the part number on it before, its an 85 psi inline pump. ill try swapping my reference point right now and see what kinda stuff happens.

Turbo11T · Oct 21, 2009

Back pressure

I hate being a na sayer. A friend and I had a conversation about this before lunch. How is your motor making boost without a load on it. I thought that a motor needed a load to make boost. Especially 8lbs. Maybe this is not the case on the 4 stroke. I have only had 2 stroke turbos.

So In turn the only way to make boost is to much back pressure. The back pressure could be what your problem is. I had a grand am one time with a plugged cat and it would lean pop really bad from the backpressure.

That is my thought only thought on this. Hopefully someone can point out why noone has brought this up about the amount of boost being obtained with no load on the motor, so We can all learn.

Thanks

Wheel House Motorsports · Oct 21, 2009

haha... ther is 0 restriction post turbo.... i was actually running an open turbo a bit ago for testing, but now I have about 4" of 2.5" downpipe with my o2 sensor in it. the thing builds boost i think cuz it does create a load on the motor to rev it up WOT, if i just ease it up it builds no boost, but if I hammer on it she builds boost then you hit your max RPM and let off the throttle and boost goes away. so there is a small load for a second as required to rev it up.

back to the carb tuning! hooking it all back up and trying something new.

Turbo11T · Oct 21, 2009

Ski-Dooin it said:
haha... ther is 0 restriction post turbo.... i was actually running an open turbo a bit ago for testing, but now I have about 4" of 2.5" downpipe with my o2 sensor in it. the thing builds boost i think cuz it does create a load on the motor to rev it up WOT, if i just ease it up it builds no boost, but if I hammer on it she builds boost then you hit your max RPM and let off the throttle and boost goes away. so there is a small load for a second as required to rev it up.

back to the carb tuning! hooking it all back up and trying something new.

Hope your not thinking I was trying to be a pain I am just eliminating possiblitys. And I don't mean restriction after the turbo I meant restriction in the turbo. In the form of to small a/r or to small of turbine wheel.

On the vector that i have the boost reference for the fuel pressure reg was on the airbox. I also read that it should come from in between the carbs and motor. So it is hard to say. I think pulling boost reference for the FPR from the carb boots might be good as with a vaccum the FPR should show less fuel pressure. And the second the throttle is slightly opened the vaccum goes down dramatically.

Wheel House Motorsports · Oct 21, 2009

yeah, it made sense to me as thats what the motor is seeing, problem being, im getting a really funky idle situation. it will high idle at like 3500 and my AFR sits at around 15, then if i tap the choke to idle it down it settles to about 1800rpm and its idling super lean, im wondering if thats a product of the fuel pressure going down at idle when thers just enough rpm to create no vaccum no boost, it runs good as its getting proper air/fuel.. and that would explain it settling down to 3500 and not wanting to go lower, but maybe not. im thinking i should at least try and get air fuel off the airbox and see what it has to say about it.

if i rev it just so i am building my full 10psi right at the mouth of the turbo, so thats good, just as soon as she hits around 9k rpm.. the thing lags like nuts.

just thinking out loud, if my reference line for my fuel pressure is way to complex and restricted it would cause my fuel psi to lag behind my boost, so its leans out as boost gets higher... yes?

as far if to small of an a/r on my turbo, Its hard, mitsubishi doesnt use the number system exactly like garret does, ill have to try and dig it up somewhere... i just know it can flow a 2.?l mitsubishi 4 banger motor to 7k i hope she can spin the little rx1 motor!

Cousin Vinny · Oct 21, 2009

I don't think what you are doing will give you any results at all,for you to change anything!! At the VERY minimum you HAVE TO install the belt and "pull" the motor to make enough boost,so you can see what is going on!! Sorry,you are going to have to go to the grass,someplace,i order to get some consistant numbers. cv

POLARIS600cc · Oct 21, 2009

Cousin Vinny said:
I don't think what you are doing will give you any results at all,for you to change anything!! At the VERY minimum you HAVE TO install the belt and "pull" the motor to make enough boost,so you can see what is going on!! Sorry,you are going to have to go to the grass,someplace,i order to get some consistant numbers. cv

Best advice you've got so far. Why are you even trying to tune it by just flippin it wideopen with zero load? Also i think 10psi at zero load is alot of boost. My duramax will do it, but thats a variable vain turbo and 6.6liters. I have never seen any fourstroke gas application make more then 3psi by snapping throttle open unless they have anti lag. I would like to hear from an experienced yami turbo guy and see what he thinks of 10psi at no load.

Not trying to be a dink, just tyring to help.

Turbo11T · Oct 21, 2009

agreed

Cousin Vinny said:
I don't think what you are doing will give you any results at all,for you to change anything!! At the VERY minimum you HAVE TO install the belt and "pull" the motor to make enough boost,so you can see what is going on!! Sorry,you are going to have to go to the grass,someplace,i order to get some consistant numbers. cv

yep find some grass

mattymac · Oct 21, 2009

Have you taken the regulator appart? I have seen where some really small stuff (like locktite, dirt, debris etc) can really mess the refrencing of these regulators when they come on. It will only take a little bit to pull it appart and take a look. Most sleds with this issue they ran fine until boost would start to climb, but wouldnt affect idle or low speed/low boost fuel pressures.

DWHalverson · Oct 21, 2009

Call me if you get a chance. I would really like to try and help you out if I can. We need this running in January for Cooke.

Dave
605-716-7606

Wheel House Motorsports · Oct 21, 2009

I have a bypass switch that kicks on my fuel pump to prime my fuel system if i havent ran it in a while, so i can sit and run my pump and when I do i my fuel pressure gauge which is right on the side of the fuel regulator sits and goes up and down by about 1-2psi... im going to pull my regulator apart tommorow and check the inside and clean it all apart. Im hopping to get out and do some on snow tuning on sunday, I was just worried there was some sort of massive error in my ways as far as setting it up. im gonna bring a pile of zip ties and clamps so i can move stuff around when im doing some on snow testing and see if i can get better results.

I did notice a small cut in one of my boost reference lines... so that may be an issue.

im still getting a really weird idle situation, it only idles down to 4000 on its own now, and afr hovers around 15:1... but if i blip the choke she settles down to right around 2000 but the afr gauge goes off the lean end ---, this is really weird and im not sure what is going down causing my retarted idle situation.

BUT im getting really good afr from idle to about 8k rpm when going WOT then it builds boost and dies off.

just trying to get it tuned closer so I dont totally waste a day on the snow

sledfvr · Oct 21, 2009

Both turbo Rx-1's I have peg the afr gauges out to lean at an idle. I don't know why that is, but I tried every pilot jet size and always went back to stock. And as they said above you are just getting some boost spike with just a primary clutch on and you can't tune these sleds until you are on the snow or grass. I had 130's in an rx-1 sidemount custom chassis with a Mitsu. TD05H turbo on it. If you leave the stock jetting in, you will be very close. Some fine tuning maybe, but only after a couple rides. I have always t'd all vacuum lines together and put the boost gauge on one end of the carbs and the bov on the other.

Turbo carb tuning

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