how to tune my 1st xp-t garret carb?

simbatheking · Jan 5, 2014

Thanks for all the good info. I've just got a few questions about the fuel line and carb hook ups. I think that the rear line on the fpr would go to the output of the fuel pump and the front one off the fpr would go to the t swivel on the bottom of the carbs usual fuel inlet. Can anyone confirm this. Also I have no idea where this line coming off the front of the mag side carb goes. Help please

simbatheking · Jan 5, 2014

nuttyn01 · Jan 5, 2014

simbatheking said:
Thanks for all the good info. I've just got a few questions about the fuel line and carb hook ups. I think that the rear line on the fpr would go to the output of the fuel pump and the front one off the fpr would go to the t swivel on the bottom of the carbs usual fuel inlet. Can anyone confirm this. Also I have no idea where this line coming off the front of the mag side carb goes. Help please

Line coming off the front of the carb is more than likely for your blow off valve(BOV).

simbatheking · Jan 26, 2014

thanks nuttyn, yes that line was for the top side of the bov i believe. i read a bit about bovs and apparently some with a nipple on the top take a vaccum line that should be plumbed between the carb/tb and cylinded so when u snap the throttle closed the vaccum will assist pulling the bov guilitine open as well as boost from the bottom of the bov.
i had the sled running tonight. ive got about 4psi fuel pressure at idle and my a/f guage is not working but it seems lean at idle. the pyros are dead even but seems to climb from 350 when i 1st start it to 600f whin 2 min or so, then i shut it off. could this be because of the low elevation at my house? 2800ft the previous owner of the turbo kit was running 300 main 15 pilot and needle clip 2nd from top. im now running 340 mains 17.5 pilot and needle clip in mid position.
what is the best way to compensate for elevation change? adjust fuel press? ill unload at 4500 ft and wot is 6000-9500ft

Spaarky · Jan 26, 2014

You can adjust fuel pressure. The easiest would be with your power jets and some remote adjusters. That much elevation change you may have to adjust your fuel pressure.

Since I am sure your next question is what are remote adjusters. Well, my old buddy Twister, found a cable adjuster that conveniently attaches to the top of the power jets. The other end mounts to your dash. That way adjustments during the day are very simple. They come off McMaster Carr. I don't remember exactly what McMaster Carr calls them. They sure are handy though

simbatheking · Jan 26, 2014

ok, thanks. i looked at my aem a/f gauge that came w the kit and some of the pins in the harness connector were damaged, so ill go see if they have new connectors at the parts store and if not, ill just solder them on and see what im getting for a/f at idle. it seems a bit odd for it to be lean with a 17.5 pilot but maybe my fuel screws are turned in too much. if i remember correctly, at idle with my n/a sleds would be about 350-400f at idle.

simbatheking · Jan 26, 2014

heres some pics for anyone who cares. its not the prettiest but hopefully i can get it to work. everything is tied up well so it doesnt rub. its a budget turbo setup since i just became a dad and bought a wake boat recently. 1st ill get it running right then worry about makin better running boards etc. this setup has
-2871, fpr pipe ref, turbo coolant fed from line at bottom of bottle and returned to cooler as per gus, home made air to snow, turbo oil run off of premix pump and premixing with legend oil 32:1. Doubled up stock reeds. Kit came w boysens but when i installed them they were warped and didnt seal at the tips. I had spare stock ones around. Total about 1500ish into the kit and head and 1400 for new crank and cyl plate. hopefully it doesnt blow!!!

simbatheking · Jan 26, 2014

also, i assembled this short block with a new crank and brp pistons 5 hole base gasket and 25 thou taken out of head squish. so it'll have to be broke in which is kinda painful since i cant get to most of the good areas where i live because they all require long pulls to get to. i pressure tested the whole system and the only leaks were at the ex donuts which are new with doubled up springs. not much i can do about that i guess

gus bohne · Jan 27, 2014

cant ell from pics but be sure you have an outside intake hole in front of turbo or better yet a snorkel thru hood. underhood air is just so friggin hot.

we tend to forget that all the holes in the front to allow air IN are useless if the air cannot get OUT. it stagnates.

fwiw, ive never dropped pilot size . just adjust mixture screw. I checked joshs BOV on his rev turbo, there is only 1 line period, only to top period. I cant even find a bov that uses 2. be very very careful.
your lean low end could be the vacum leak of this weird bov
Gus

simbatheking · Jan 27, 2014

Thanks Gus, there is lots of venting. I will show more pics later. I shot some air in the top line of the bov and it moved the guillotine a fly shiit In the closed direction and no air released out the bov. Then I pressurized that intake tube and the guillotine would open at about the same pressure consistently. There is only 1 line on the bov that was my bad. There is another line plumbed to the intake tube right behind the bov for the boost controller. If there was an air leak in the bov which is plumbed just to the mag side wouldn't that side be hotter? I will try adjusting the air screws or gaining some elevation. Does air screw adjustment still affect up to 1/8 throttle pos or just idle?

swrev · Jan 27, 2014

Looking good.

gus bohne · Jan 27, 2014

yes it does.

well done

simbatheking · Jan 27, 2014

well, this is disappointing. with 17.5 pilots i had the mixture screws turned out 2.25 turns and it was real lean. i fixed my a/f fuel guage and was getting 16:1 a/f and pyros were hitting 700 at idle at 2800ft!!! i turned out the mixture screws to 4 turns and that seemed to help a bit and got a/f ratio down to 15.4 but pyros still hitting 700. i played w the fuel press a bit and had it up to 8psi but that didnt seem to change the temps that much. i think its safe to say something is wrong. the million dollar question is what. i pressurized the system again to check for an air leak but didnt find anything. i might have to do a more thorough check tho. i blocked, the line comin off the mag carb and that never changed anything. if anyone has any ideas thatd be great.

simbatheking · Jan 27, 2014

is there anything that could cause the carb float level to be low or anything that could be wrong with the carbs that anyone can think of?

islanddoo · Jan 27, 2014

You definitely have a leak somewhere. I run 15 pilots at 1.5 turns out w/350 mains and 2nd clip on pilots. Run at 3k to 6k in elevation never over 1200 deg and idles nice at sea level with afr's at around 15 and 14.2 or so when unloading. Running about 4 to 4.5 psi fuel pressure. Check the intake boots very carefully they tend to delaminate from the inside. Also check the carbs for any blockages, or debris.

gus bohne · Jan 28, 2014

never use your fuel pressure to tune air fuel ratio,,, this IS NOT efi.
When you try that all you are doing is starting it in a flood . you are using fuel pressure to bounce the needle and slightly folood the engine. BAD!!!!

float levels can be off but it would require a heat gun to bend the plastic .

aaa did you use your carbs ? or did it come with them.

check boots really good. something is up.. dont try to ride it till you get this under control as whatever is causing this will take you down in the field.

are you turning the white plastic knob out on the carbs or the AIR SCREW <<< air screw is IN to make richer ..white capped screw is OUT to be richer..

Gus

simbatheking · Jan 28, 2014

im using the carbs that came w the kit. they were already setup w powerjets and looks to be done as described in the r&d turbo instructions.

i tried some known good stock carbs that had all stock jetting which is same pilot jet and idle screw 2.25 turns out same needle and a 480 main. this resulted in much richer running to where it seems normal again. once it warmed up it settled at 14.4-14.5 a/f and 540-560 egt which seems acceptable. this makes me believe the problem is in the carbs.

i also tested it with and without the airbox just incase that was f'ed since its an experimental airbox. it was slightly lower egt w airbox by 20 degrees or so and same a/f so not a prob.

now to figure out the carbs, i guess ill have to pull them apart. any input is always appreciated.

yes i was turning out the screws w white knobs.

gus bohne · Jan 28, 2014

GOOD CATCH !!!

now pull the power jets from that set of carbs. trim the brass tubes and mount them in the bell or in the airbox connector tubes to each carb.

i have found 2 sets of DAVE crabs that did the same thing AND would not run on boost at all..blew up cconstantly. he did something maybe the power jet placement i dont know, but when things arent working right,,, replace the offending component.

turbo800 · Jan 28, 2014

I've never seen powerjets mounted in the slide cavity of the carbs before. It would seem that the brass tubes would have to be pretty short to not hit the slide at full throttle. I'm guessing they were put there because of the short distance between the airbox and the bell of the carbs.

Personally, I would notch the clamp on the bell of the carb and move them there and plug the slide caps!

simbatheking · Jan 28, 2014

ok, then do i copy everything else the same way the r&d carbs were set up the 4 lines going to the airbox?

how to tune my 1st xp-t garret carb?

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