Thread: 259cc @ 4bar safe for ~200whp? help

hi all, i have a RR DE, so i cant use 370cc, or any side feed
any top feed MSD will require a tuned ecu
im trying to avoid that for now,

stock top mount 259cc injectors wont flow enough at stock 3 bar to support stock boost from a T25 set up.
Using a SAFCII and use a fuel press. regulator at 4 bar (59psi) ill be in the +200whp safty range, being its not after market inj. it will run 4bar.
i know safc can operate 50% over stock injector capcity, way more that enough tuning room for the fuel pressure increase.

so heres my formula,
259(29/37)~204 ----------29 divided by 37 multiply by the cc (259) and thats the 4 bar estimate?
i dont know where that guy got his numbers from...
http://www.sr20forum.com/1805822-post62.html

but then again, 44psi is 3 bar, 59 is 4bar, 4 bar is only 34.5% more than 3 bar
so shouldnt it be 259+34.5%= 348cc = 250hp?


roughly 204 hp, thats a safe range for a T25 set up.
or is it 250 hp?

wait whats this, http://zilvia.net/f/tech-talk/134996-afr-injector-size-thread.html
Flow Rate = (HP x BSFCX10.5)/ (#injectors x Max Cycle) to find inj cc needed at 80% max cycle
sr20det is .55 BSFC, according to him. i cant find a det BSFC any where online tho. wiki says a trubo engines BSFC is .8!



i added 50hp at the flywheel bc of 25% loss at the a/t transmission

so (200 x .55 x 10.5) / (4x .8 ) = (1155)/(3.2)= 360cc

328cc is the minimum to run 200 hp but wait, 370cc says its good for 250whp
http://www.sr20-forum.com/1315-post1.html

but isnt the cc the cc? even if i change the FP it wont change the max out put, just the FP, only will help atomization? kind like a clogged drain, wont flow more volume, just will squirt out harder?


i must be missing something, help me please im really confused!

259cc inj at 4 bar = 203 WHP.

I would not run the T25 on stock injs. You will out run them at about 6-7 PSI.

If you need some injs info.

http://www.sr20-forum.com/information-library/166-inj-size-whp-output.html

thanks for writing that thread, i refer to it alot
could you give show me the formula u used to get 203WHP?

here is some back ground info: W10, Automatic 2001 p11, SAFCII, LM2 ect

i also found another formula from another member:

more fuel pressure will make ''pass'' more fuel for the same cycle or injection time. So if you have
-10ms ot inj time at 3 bars they will put ex 259cc
-10ms of inj time at 4 bars they will put--- 259/3 = x/4

so 4x259/3
= 345 cc approx

Fuck it. Run 5 bar of fuel pressure. A few folks around the forum have run anything from 4 to 5.5bar of fuel pressure. At that point it's more about the pump or fuel delivery than the injector itself.

Consider this.

If you have a bottle of dish liquid that has the small opening on the top if you fill one with water and turn it up side down it will drain out at a given time. If you squeeze the same bottle it will drain out much faster because of the outside presure you applied.

Think of a given turbo, It flows more air at 10 psi than at 5 psi. That being said the inlet and outlet of the turbo has not changed just the presure. At the same time the diffrence in flow from 10 psi to 5 psi is 100% but the diffrence in flow is not 100% more.

The formula is Presure X Time.

thanks for the insite in laymens terms, i understand it now, props!

5 bar sounds like it will pop a line lol, im running a 255 pump so i know it will coast on that

a 255 Walbro pump without an aftermarket FPR generally runs at 53-56 PSI

Why not just find some 20v or vet injectors, Pretty sure they are direct replacement for the RR topfeeds.

Check around the for sale section, i think Sealti96 may have some that he would sell. Miko would know what size the 20v injectors are

I have injs listed below which are all a direct fit for the top feed RR motor


20V 350cc Injs = 240 WHP = $120
VET 444cc Injs = 299 WHP = $200
GTR 570cc Injs = 380 WHP = $300