JOE3 Posted December 27, 2003 Report Share Posted December 27, 2003 I'm looking at running 30psi of boost or better on my MPI. What size injectors are you guys running and where can I get them at a good price. Link to comment Share on other sites More sharing options...
Ben_D Posted December 28, 2003 Report Share Posted December 28, 2003 But what size turbo? It will make a diffrence depending on the CFM rating of the turbo. What sort of hp?? But if you plan on shooting for 400HP you will need at least 750s of 72lbs Ben D Link to comment Share on other sites More sharing options...
eeaston Posted December 28, 2003 Report Share Posted December 28, 2003 I'll second that. The corellation between boost and fuel requirement isn't direct. You need to base your flow rates on your horsepower target. From SDSEFI's tech page: http://www.sdsefi.com/ffhp.gif The third column is attainable horsepower at 100% duty cycle. You should size your injectors to run at no more than 80%, so multiply those HP numbers by 0.8 to get an idea of how much HP each size will safely support. Like ben said, 72's are good for 0.8 x 524= 419.2 HP. I along with a few other guys are running 72's or 75's with decent idle and plenty of fuel for 400 HP. I got my matched Siemens 75 pounders at racetronics for $60 each. The same size Delphi(MSD/Holley) injectors were a couple of bucks cheaper. http://www.racetronix.com/ Link to comment Share on other sites More sharing options...
JOE3 Posted December 29, 2003 Author Report Share Posted December 29, 2003 I,m running a T3/T4 that flows 650cfms @15psi. I think the 750's will do. Thanks. Link to comment Share on other sites More sharing options...
Boosted_One Posted December 30, 2003 Report Share Posted December 30, 2003 I,m running a T3/T4 Â that flows 650cfms @15psi. I think the 750's will do. Thanks. Ya go with the 75lb injectors. I used Holley FI about $82 each. eeaston has a source for some decent 75lbers too for a very good price. 550's will not be enough IMHO 650's would be the least I would run. Go bigger though, you'll grow into them. Link to comment Share on other sites More sharing options...
heefner Posted December 30, 2003 Report Share Posted December 30, 2003 I'm running the siemins 72 ponders as well. IMHO they will give you plenty of fuel and still be tunable to drive on the street. Eric thats a really good price. Link to comment Share on other sites More sharing options...
eeaston Posted December 31, 2003 Report Share Posted December 31, 2003 I'm running the siemins 72 ponders as well. Â IMHO they will give you plenty of fuel and still be tunable to drive on the street. Â Eric thats a really good price. Yes, I am the king of cheapskates! Link to comment Share on other sites More sharing options...
Joel Posted December 31, 2003 Report Share Posted December 31, 2003 Be aware, I have not proof of it yet, But I think you'll need more injector than any of those charts tell you. Most of them assume a .55-.65 BSFC, and I personally think we are getting lower than that (like .45). These machines aren't known for their extremely high efficiency. I'm seeing right now on my 800cc/min injectors points in which I require 45% or more above 4000rpm to maintain a 12.5:1 AFR as reported by my wideband/datalogging. I dont feel that at 15psi on a 16G that I'm making much more than 250hp, especially at 1 mile up in altitide. Just keep it in mind. 400hp would certainly be within a 750cc-800cc injector. Joel Link to comment Share on other sites More sharing options...
Boosted_One Posted December 31, 2003 Report Share Posted December 31, 2003 Be aware, I have not proof of it yet, But I think you'll need more injector than any of those charts tell you. Most of them assume a .55-.65 BSFC, and I personally think we are getting lower than that (like .45). These machines aren't known for their extremely high efficiency. I'm seeing right now on my 800cc/min injectors points in which I require 45% or more above 4000rpm to maintain a 12.5:1 AFR as reported by my wideband/datalogging. I dont feel that at 15psi on a 16G that I'm making much more than 250hp, especially at 1 mile up in altitide. Just keep it in mind. 400hp would certainly be within a 750cc-800cc injector. Joel I'll second this. When I went to WB I increased the fuel amount quite a bit! More than you would think with 75lbers that's for sure. Link to comment Share on other sites More sharing options...
JOE3 Posted December 31, 2003 Author Report Share Posted December 31, 2003 Thanks for all the input. I'm looking to get 400hp. Last time I dynoed my quest it dynoed at 273 to the wheels. I run 3 extra injectors on an injector driver. But I run out of fuel at high rpm. So with the input I get from you guys I can get the right injectors to keep from leaning out when I install my MPI. Looking to get out of the 8's and in to the 7's in the 1/8 mile. 1/4 mile is a little far for me. I have two 1/8 miles closer and I get more passes. Link to comment Share on other sites More sharing options...
pinale69 Posted January 6, 2004 Report Share Posted January 6, 2004 I'm running the accel 72# (700cc) injectors, they are really seimens that accel flowed and matched and put their sticker on. I'm running an 18G and get plenty of fuel. but yes, our motors aren't very efficient, sds suggested I run "70" on my injector flow setting for my displacement and injector flow, but I actually had to set it to 87. well, my mbc messed up on me, so for a full day I was pushing 30psi and had a few knocks which had me worried, but never went lean, and I was hauing A$$. probably upper 300 hp range and no shortage of fuel in the 6000rpm range (tim c mechanical lifter cam and the schnider springs really wake up the high rpm). and serioulsy I was probably putting close to 400 at the flywheel then. but keep in mind, I got some stock compression ratio wisecos, and that is probably the only reason it didn't blow up Link to comment Share on other sites More sharing options...
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