What Injector Size for 400hp ? - Perth-WRX.com

maddog · #1 27-10-2007, 02:06 PM

Whats available and recommended for side fed injectors for a MY99 to support 400hp atw? Want < 85% idc @ 43psi fuel pressure.

edit in summary:
Here's the feedback from Sam Rigoli confirming they can hi flow the yellow top 440cc side feed injectors :

Hi Morgan,
Yes we can hi flow them. The hi flowed ones can support up to 500hp. To do the four injectors your looking at $520.

Regards,

Sam Rigoli
Unit 11, 7 Birmingham Avenue
Villawood NSW, 2163
Sydney, Australia
Phone: +61 2 9727 0695
Fax: +61 2 9727 4697
www.tonyrigoliperformance.com.au
sales@tonyrigoliperformance.com.au

teejay · #2 27-10-2007, 02:32 PM

I think 850cc injectors will suffice. As for brand, not really sure.

vyper · #3 27-10-2007, 02:36 PM

Have you got the injector size calculator - By Autronic I believe. Good to give a rough idea of what you will need.

Have a quick browse through one of the previous injector threads, or PM me your email and Ill send it through.

Put some numbers into it then, and says anything 800cc + ...

WRXTASY · #4 27-10-2007, 02:56 PM

I've saved this from somewhere else Morgan:

Quote:

Formula I have to work out max power for injectors is as follows:

CC of injector divided by 5 x how many cylinders = Max BHP at 100% duty.

So 440cc injectors in a 99 will equate to a max BHP at 100% duty cyle of 352. Obviously I need to have a safety margin for acceleration enrichment and so forth so a max of 80% duty cycle would be very safe.

352bhp minus 20% is 281.6bhp which is just on 210kw's.. Given the common 15% drivetrain loss that would be about 178kwatw.. not enough...

550cc injectors will give me 223kwatw at 80% duty cycle

650cc 265kwatw at 80%

800cc 325kwatw at 80%

I went through this a while ago and took Tuna's advice to do the GD Throttle body + Manifold + cheap top feed decaps with the Motec M800.
Its a bonus then that you can then run AVCS with Spare AUX ouputs that the GD Throttle body provides.

trainwrex · #5 27-10-2007, 03:17 PM

hmm 800cc at 325kw atw... close to what im wanting..

hmm so my 1260cc injectors are around 1008hp

are u sure this is at the wheels??

maybe i should have just stuck with the 800s. How accurate is this calculation??

Hurtenstein · #6 27-10-2007, 03:21 PM

Quote:

Originally Posted by WRXTASY

Its a bonus then that you can then run AVCS with Spare AUX ouputs that the GD Throttle body provides.

Cant you just run avcs off a rev activated switch like a shift light?

Mat · #7 27-10-2007, 03:50 PM

Quote:

Originally Posted by trainwrex

hmm 800cc at 325kw atw... close to what im wanting..

hmm so my 1260cc injectors are around 1008hp

are u sure this is at the wheels??

maybe i should have just stuck with the 800s. How accurate is this calculation??

Keep the injectors and just chase more power

tuna · #8 27-10-2007, 05:50 PM

Quote:

Originally Posted by Hurtenstein

Cant you just run avcs off a rev activated switch like a shift light?

nope

tuna · #9 27-10-2007, 05:53 PM

i remember hitting 100% duty at 460hp with 816cc injectors, only issue was the single 4 year old walbro fuel pump had insufficent pressure & volume to maintain flow.

so even if you went bigger injectors, you'd still need a much bigger (or multiple) fuel pumps to keep such large injectors under 80% IDC.

madmax · #10 27-10-2007, 06:56 PM

chasing 800+'s as well... for a 97 ra - old side feeds

If anyone finds a good deal/source for a set, could you please post in this thread.

edit - forgot to list the year of the vehicle