Shortly will be installing the 2.87 and would like to find out from those that already have the set up what there experiences with it have been..Do anything besides a tune to keep it safe? Added W/M.? Any problems to report? Overspinng the blower problems?

Anything useful is appreciated.

 

My fuel setup ...

Walbro 255
FunctionTUNED Fuel Return
DW 600cc Injectors

Check the link in my sig, there are more details there.

For you, I'd upgrade to at least 500cc injectors and you should be good. You will be overspinning the blower at about 6500RPM and up IIRC (again, check the calculator in my signature for the exact overspin point).

And yes, you will need a new tune.

 

if your sig reads correctly take off your 34t j/s cog and put the 32 back on when you install the 2.87 serp pulley. if not you will definately be over spinning the blower plus your engine will be working harder due to less mechanical advantage with the 34 to 28 cog setup and also you will most likely see belt slip with a 34t j/s cog pulley and a 2.87 serp, i know i did. i lost power when i tried that setup. 32/28/2.87 is the winning combination.

 

interesting comment about losing power.

That would go on to say that running a 32/32/2.87 might be better yet as you get more mechanical advantage

 

That sucks, not many people have blown their stock motor with the 2.87 pulley. The ones that I read about were a result of a bad tune or prior engine damange ... what was yours attributed to?

 

Overspinning is a given..With the 34T j/s & 28 cog & 3.12 pulley the blower RPM is 53.3k with a 6600 rpm shift point. With the 2.87 and same shift point the blower will see 58k..With a 32T j/s and 2.87 pulley the blower will see 54.5k

Less mechanical advantage has me scratching my head to understand why? A small additional load on the engine due to the fact that the blower will work a little harder to compress the additional air?

Also your loosing power was attributed to what? Belt slippage?

 

yes it would be better with a 1 to 1 drive but with this being said the blower rpm would be greatly reduced and the boost would come in quite a bit later in the rpm band. the 32 j/s cog,/28 s/c cog and 2.87 is a good compromise. when i last tuned at GTM we tried a 34 j/s cog 28 s/c cog 3.12 serp configuration. then we swapped to a 32 j/s cog, 28 s/c cog 2.87 serp and gained about 20 rwhp just with the pulley change. i arributed it to the mechanical advantage the pulley system offered with the 32/28 ratio opposed to the 34/28 split. to put it in laymens terms if you are riding a 10 speed bike and you go from a large front sprocket " sprocket on the pedals " and then to a small sprocket on the rear wheel it takes you more pedal force to get the bike initialy moving. once you select either a smaller front sprocket or a larger rear sprocket it will take less pedal force to get the bike initialy moving. hope that makes sense.

 

chalk that one up to a shitty base map maybe?

 

I would stay with the 440cc inj if you have the RFS, deff get a retune and not to exceed 11.5-12 psi with the 2.87p whatever rpm that may be.
Use the utec to limit the rpm.
Also recomend (Bando belt & gtm idler setup).

 

the graph on the left is the 32/28/2.87 pulley setup. the graph on the right is with the 34/28/3.12 pulley.

BTW the graph on the left was not my final pull and tune. there were some belt slip issues due to a brand new belt being installed at that time. we complied with a couple of more pulls, re-tightened the belt and performed the final tune. unfortunatly i do not have that final dyno graph on my work computer. the final pull was the same hp output but i gained 10 more foot pounds of torque. sorry

 

Hard to read the a/f ratio on run 23 but it looks like it was lean on fuel..Was there any fuel trim's made to run 31? It does not register to me that going with a 2 tooth larger J/S would or should make any measurable difference in power particularly a loss..

 

well i am just letting the forum members know what Sam from GTM and i have found out from several dyno run's with different pulley configurations. i am not here to debate the matter, if you do not belive it than oh well. and i do not mean that in a disrespectful manner.

 

I have the 2.87, but havent picked my car up from Forged yet. Will update you with my thoughts shortly.

 

I do appreciate your comments and no offense was meant however, I have difficulty in understanding a loss of power when the gearing and ratios are intended to make the blower spin faster thereby pulling more air (oxygen) into the intake to produce a bigger bang..

Now, I havent looked at the blowers efficiency maps yet but a loss in power or significant loss in efficiency by spinning the blower an additional 2k rpm would not be a reasonable explanation for a loss in power. However, at the same time due to increased temp (heat of compression) may not produce the potential power increase it would in a larger blower or even a higher efficient I/C..I kind of suspect your experience has other factors going on that may explain your results.

 

well go ahead and do both and a see for yourself. only takes a minute to swap the JS pulleys.

 

What I'm thinking on doing is with the 34T J/S, swap the 3.12 with the 2.87and Dyno tune...Remove the 34T J/S and put the 32T J/S on and see what difference it may make on the dyno.There is apprx. 6.5% difference in blower RPM between these 2 configurations. I prefer to keep the Blower RPM as close to its advertised limit as reasonable.

My overall goal is to pick up about 20lb-ft of Tq above what I now have which is 310lb-ft..(DJ) The 34T J/S and the 2.87 might get me there if I assume a 30% loss due to heat and non linear blower cfm (inefficiency).

 

bump... would like to know if the 34T and 2.87 are a good combo for non revup motors. I know it's bad on a revup motor but I remember booger telling me he gained a lot with the 34T.

 

I think that will be a great combo with an upgraded Impeller.....

 

ya i was thinking that too

 

a T-trim and that pulley combo would be nice! top 500 easily i'd bet with some good timing.