GT2876 Test result

utah_sledder · Dec 24, 2011

Well I just got back from a test ride with a 2876. I got it with a .64 turbine housing. It builds boost really quick....that being said it is definitely not quicker than the 2860 that I was using last year. It is probably about a 1/2 second slower than the 2860. It does start building boost at about 6200 RPM and cruising it is running about 3 lbs of boost. The 2860 is building boost almost immediately after engagement which is around 5500 with white/white spring. I have my boost controller set at 8 lbs. From 3lbs to 8lbs the 2876 is really fast. One of the things I noticed is that my EGT's were way down from last year running the 2860. I assume this is from the bigger compressor pushing cooler charge air. Cooler in=cooler out. I think that I can probably improve the response of the 2876 even more by leaning out my mid range a little bit. It feels pretty fat from bottom to mid (at 10,000 ft elevation). I have the '07 needles in the middle position.

Anyway, just thought I would share my experience.

pus1100 · Dec 24, 2011

.64 ar?would this be to tight for 800 2 stroke.thought .86 ar. was the recomended for 800's?

Boyko · Dec 24, 2011

You got to much exhaust pressure because of the tight turbine housing

Swap the .86 housing onto the 2876 then see what happens

swrev · Dec 24, 2011

I see you also installed STM valves in another thread, and are fighting to get peak RPM, let us know if that makes any difference on the responsiveness once you have that figured out. I would like to try a bigger turbo also, but am not totally convinced it is the way to go although the concepts being talked about relative to sizing, boost, and temps all seem logical.

gus bohne · Dec 25, 2011

.64 !!!!!!!!!!!!!

we have boost UNDER 4000 rpm wtf are you doing bogging at 6000 ??

You have marks valves and your engaging that high,, somethings way off man..sounds like the jetting .

keep us posted,,

Gus

utah_sledder · Dec 25, 2011

.64 housing hmmm, did quite a bid of reading and thought the consensus was to put a smaller housing on the big turbo to get it spinning quicker....Oh well easy to swap to an .86 after a bit more testing. Anyone have a used .86 turbine housing they wanna sell cheap?

Gus, no bog but found the best response with engagement at around 5000 rpms. I tried many different clutch combos last year and found that anything less than a 230 start (4800 engagement) was breaking its back. It was just too tough for the motor/turbo to overcome the load, and made the sled really sluggish.

I threw the stock rave vales back on last night to test on the next ride. I want to eliminate all variables until I get the big 2876 dialed in. Then I will put the supreme tool valves back on and start working on the spring tension to get them to open when I want them to.

gus bohne · Dec 25, 2011

What IS the model of the sled in play here .?
rev, xp , e torch ?

have a rev and xp engaging at 3400 rpm with instant boost ,, I mean instant...

Gus

Boyko · Dec 26, 2011

.64 gus, I always thought that would be to tight but I am always chicken to try something different:face-icon-small-blu I can see that spooling up pretty fast but isn't there a trade off some were. I tried running a tight areocharger 10 years ago and found it hard to tune. What kind of pipe pressure are you seeing? Is there a lot of 2876 running a .64 out there?

utah_sledder · Dec 26, 2011

The sled is an '08 XP 800R. Ran a GT2860 all last year (2300 miles all over 7000 ft elevation) with great results. But all this talk about lower charge tube temps got me thinking that a bigger turbo would cool things down a bit.

Not to argue but I tried low engagement last year (3600 rpm engagement) and it was doggy as heck. It took WAY longer to spool than the higher engagement. Riding in the trees was a nightmare, if I didn't have the engine reved up it would take forever to get boost back. That ride was at 9500 ft elevation. Switched back to the 5000 engagement and bam engine/turbo is right there all the time.

fredw · Dec 26, 2011

i would think as well gus that that low of engaement would not work well for tree riding, spool up time is very important an 10k feet, not like running the flatlands

gus bohne said:
What IS the model of the sled in play here .?
rev, xp , e torch ?

have a rev and xp engaging at 3400 rpm with instant boost ,, I mean instant...

Gus

gus bohne · Dec 27, 2011

Not yes.. NO on the .64 way to tight ...never !! I have tried the 30 with that ar and it worked much better..4 psi over in pipe.

I always spec the .8 hot side for the 28 housing..

I can understand the alitude needing more eng rpm, but with the valves I still dont see the need for 5000...there are so many ways to work a ramp and stem combo that you can engage low and not load the eng to hard..

FRED, you were looking for the snox cluctch,, that has a .080 shorter post to tuck the roller and make it as ZOLTAN would say,, silky smooth !!!!

these new tra jumks with the taper are NOT as tuneable and make you have to grind your own ramp..

I wonder why the other guys are loving them and your having trouble,, makes me wonder what else is different ,,,something seems fishy..

to bad the sled is not running as usual , you stated the valves were not tuned yet, you could not get rpm on top ? I am NO fan of them, Bryces solution is dandy.. Marks stuff is either aw

some or,,, well not so good..hummmmm that hot side must be driving the back pressure to over 7 psi,, thats too high for good riding, Want to sell the turbo we can give it a good home with one of the many twisted guys looking to upgrade..
Gus

Octanee · Dec 27, 2011

i can see the need for higher engagement, due to high elevation, sled would have alot less power, and it probably would take more for it to build boost because air is thinner? (shot in the dark here)

utah_sledder · Dec 27, 2011

Well went for another test ride today. The snow really sucks so it's pretty much a really long road ride with one hill that I can test on but that's better than nothing.

I got a few gremlins worked out, found a few air leaks and got them all fixed. The sled easily pulled 8200-8300 RPM today. All I changed was the Rave valves back to stock and fixed the air leaks. Now that I have a pretty good baseline I will start messing with the Supreme tool valves (these are the replacements for the bellows).

The 2876 pulls like crazy. It still is slower than the 2860 to build boost but I'm getting closer. It feels fat in the bottom to mid so I leaned out the needle one clip ('07 needles) for the next ride. I really think my response will improve with the leaner bottom to mid.

One thing I would like to know...Gus...Bryce...what does a tight exhaust feel like? What should I be watching/feeling for with the .64 vs the .86 turbine housing? Will the response simply get better or does it show up on the egt's or does the power fade? What's the symptoms of too tight of an exhaust?

turbo800 · Dec 28, 2011

gus bohne said:
Not yes.. NO on the .64 way to tight ...never !! I have tried the 30 with that ar and it worked much better..4 psi over in pipe.

I always spec the .8 hot side for the 28 housing..

Gus, Is that a yes or no on the .64 a/r too tight for the 2876? I can read it both ways by your reply...

Great comparison utah_sledder!

I'm running the Mitsu 7cm2 housing. Nearest I can tell by comparison charts its close to a .49 housing ((CM x 8) - 7) / 100 = a/r ratio. There's a few variables at play, so I'm not positive on that number.

I think one drawback of the tighter housing is you will see increased EGT's for longer pulls, not letting it shed it out the exhaust stream as easily.

utah_sledder · Dec 28, 2011

turbo800 said:
I think one drawback of the tighter housing is you will see increased EGT's for longer pulls, not letting it shed it out the exhaust stream as easily.

I agree with ya on that. I spoke to Bryce about it the other day and he said that it would mainly show itself on a long pull. It should show up on the EGT gauge though so if it starts getting too hot it's time to let out.

I am still curious about the response difference between .64 and .86. Guess i'll have to be the test mule.

Eli · Dec 29, 2011

turbo800 said:
Gus, Is that a yes or no on the .64 a/r too tight for the 2876? I can read it both ways by your reply...

He is saying no to the .64 on the 2876 and yes to the .64 with a 30 series (3071/3076) for 800 class sleds.

gus bohne · Dec 29, 2011

Utah, we only like to see about 4 psi over boost in the pipe, so the .64 is going to take you past that at some point in your boost build,, dont know where,, you will have to find that..

the other possible issue is low flow before boost hurting response, like having the vanes shut on a variable,, no flow,, no go..

the dynotech trip was great..

back home at 1 am,, still grinning like a theif..

Gus

Eli · Dec 29, 2011

Like a potato stuck in the tailpipe of your Mom's station wagon! :bolt:

brycter · Jan 6, 2012

update..... utah took off the big 2876 and is going to put on a 2871. should work alot better for him. .86 housing. JMO:lalala:

gus bohne · Jan 6, 2012

WOW, you just keep getting nastier every time you post Bryce,

first it was outlaw addict and your backhanded bs
now this...

very disappointed

gus

GT2876 Test result

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