Quite possible they're putting too much fuel in, not uncommon on E85 tunes. Also power on E85 is made through adding timing. Without adding in timing the power output on E85 at the same lamda is not going to be far off what you would make on 98. Can't remember exactly but once we'd tuned the fuel maps mine made around 40-50rwkw just on timing, and we kept it conservative.
As a guide, I got 285RWKW with just high flow turbos and 555cc injectors on a freshly rebuilt engine without being properly tuned.
https://www.deatschwerks.com/fuel-calculators/fuel-injector-calculator Just punched in 469hp plus 20% drive train loss (563hp) in this calculator and come out to 736cc injectors at 87% duty cycle on e85
Your maths is a little off -469 is 80% of 586 crank hp. Which on the same calculator recommends 766cc injectors to achieve that power at 87% duty cycle. Splitting hairs yes but relevant to the question of 740cc injectors being a “good” choice for a motor making 500rwhp on e85. Duty cycle really should not exceed 85%. Another “rule of thumb” is to divide injector flow rate by 5 which gives a theoretical max HP per injector. So your 740cc injector can flow a theoretical 148hp, which allowing for 30% more fuel on e85 is a theoretical maximum of 113hp, which is 96hp at 85% duty cycle, which is 77hp at the wheels, which is 464rwhp in a six cylinder engine. Note this does not take into account forced induction which will require more fuel than an NA. The Deatschwerks calculator suggests 442rwhp maximum for 740cc injectors on e85.
After all the fuel system issues I have had, I'd rather have too much injector than not enough... This is also helpful because you can control injection timing around valve open time, but less of a concern with an ecu that can't control injector timing.
My 300rwkw setup below: 1000cc top feeds 3" split dumps 2.5" exhaust 2.5" cooler piping Big smics Nistune E85 18psi dropping to 14
This, why argue over 740cc, 1000cc side feed are on the shelf in Australia with S1 adaptors https://www.ebay.com.au/itm/6-x-100...VG30-upgrade/132314230694?hash=item1ece8aefa6 1200cc side feeds can be imported, using the above cal 950hp at the crank on e85 at 90% duty cycle https://www.ebay.com.au/itm/1200-cc...176661&hash=item3ab1a4e8ee:g:j8kAAOSwHmhV8wr2 haltech seems to drive large re manufactured side feeds fine, nistune hit and miss although Iv only read bad reports from straight six and sr setups . If you need more injector than this go top feed.
Sure but OP is talking 300-350rwkw. 1000cc drilled injectors are much bigger than is needed. 740's will handle that range comfortably. 90-95% duty cycle isn't a problem. I ran my 20yr old stock injectors constantly to 100% peak duty cycle before upgrading and never had any issues. I'd be more concerned running aftermarket modified injectors to 85% than I would genuine unmodified injectors to 95%+. If you've got the money to buy all the fancy bits you don't really need than fine, but why spend more than you need to.
Its a tough desicion, i'd be happy with the 740's as long as it dose'nt lean out the A/F mixture as i think that's what killed my engine
Redrilled injectors are one way of doing it but they have horrible tuning resolution and fuel atomisation. Probably not an issue when comparing peak power but economy, low load, throttle response etc... I wouldn’t go planning to run your injectors up to 95% duty cycle in that case...
Remember peak duty cycle is exactly that, peak. You're only seeing it very briefly at WOT and full load. If 20 year old factory injectors can handle bouncing 100% duty cycle constantly at the track, aiming for 90-95% peak duty cycle on quality injectors isn't a big issue. If you already have 740's I'd just add Nistune, high flow or similar upgrade, big SMIC's, EBC and tune to what you feel comfortable to with those injectors, will get you into the low 300's at least. This is the least expensive option. If you've got money to burn go top feed, Link ECU, and all the goodies
I made 387rwkw on a rolling road dyno with 740cc nismo injectors and 2860RS turbos doesn't mean I'm not going to go bigger.
What fuel? Even with 15% drivetrain loss and running super lean you’d need to be at 120% duty cycle...
