imitek

Its info i wanted to no because some are running 100% and wanted to no why it was bad idea and now have plenty of reasons to not run 100% now thaks to you guys

RotaryEvolution

iTrader: (30)

you'd be surprised how many vehicles are setup with limited injector sizing, and eventually everyone wants more power. best thing is to just upgrade the injectors but even in a perfect world you sometimes hit walls earlier than expected.

imitek

Ok next question since uve all been helpfull this far
Can u not just increase fuel presure to get the more flow or is that putting to much presure on the injector solnoid closing

Liborek

Yes, you can. There is no rule that you must run xx psi base pressure. Then it depends if your fuel pump can flow enough at higher pressure, as flow of pump goes down with higher discharge pressure - restriction.

Surely its better to retain positive and predictable control of injectors with higher delta pressure, than running at 100% duty. There must be some reason why injectors can operate with 100+psi delta... Better atomization comes to mind, but Iīm not going to speculate

RotaryEvolution

iTrader: (30)

generally it is because it becomes more difficult to control lower duty cycle injection at idle speed.

additionally, the more you labor the pump system the more you heat up the fuel, the less power you make, the more prone to issues you will be having.

FullFunctionEng

iTrader: (13)

Care to elaborate on that second point?

F1 cars used to run fuel heaters in the turbo days to increase vaporization of the fuel, thus increasing power. I have an SAE paper on it somewhere... Obviously you don't want to take your fuel system to the limit, but as long as they're designed to handle it, increased pressure isn't a bad idea. Many people have had great luck running 100+ psi with the Bosch 044 pump and ID injectors. The superior linearity and dynamic matching make the ID's very easy to tune at low pulsewidths even at high pressure.

RotaryEvolution

iTrader: (30)

we're talking about mainly street driven cars i assume. most pumps are meant to stay cool and not be labored that much.

not everyone runs new style injectors so atomization will vary depending on the temperature of the fuel.

for the most part the system is just not made to run that much pressure, yes you can do it but for how long and with what results? that is alot of pressure for a street driven car that isn't inspected on a daily basis, possibly rupturing lines or cooking pumps at the worst possible time.

if you maintain higher temps and can have system integrity then there is no drawback, but who is really going to do all that for a non F1 car? they also don't use pump fuels having a higher anti knock threshhold. they push the limits to get the most out of whatever they can, that does not mean it is a reliable method for daily use.

Trots*88TII-AE*

iTrader: (11)

It's called "Honda Formula One Turbo-Charged V-6 1.5L Engine", by Otobe, Goto, Miyano, Kawamoto, Aoki and Ogawa. Honda R&D. Paper # 890877



This figure is the part concerning fuel temperatures. As fuel temperature increases, power output does eventually go down. Not to mention as temperature goes up, the fuel's ability to reduce intake/combustion temperatures is also reduced, and potential for pre-ignition increases. What they were more concerned with was the decrease of BSFC from heating the fuel, which was the reason for doing it.

FullFunctionEng

iTrader: (13)

That's it! Guess I should have looked it up again before sticking my foot in my mouth... It was BSFC, not power . The temps they are dealing with are pretty ridiculous though, and I suppose you would need a fuel with fewer hydrocarbons to even consider going above 60*C as I'm sure pump gas wouldn't handle it so well..

In any case, as long as you design the system to handle the higher pressures, it will be fine.

Liborek

We should point out that power in this particular test varied less than 1.5% between 40°C-90°C. This easily can be accounted by change in density and hence energy content in given volume. So we canīt say that hot fuel on its own is detrimental for power production.

https://www.rx7club.com/forum/showpo...91&postcount=6

Most significant part of charge cooling comes from latent heat of evaporation which has much higher magnitude than heat capacity of given fuel. Yes, calculated temperature drop is higher with cooler fuel, but cooler the fuel is, higher the chance that significant part of it is just wetting the runners and receiving heat from them, not from air. Consequently temperature drop is lower.

I know it seems counterintuitive, and in case of pump gas which has low boiling point fractions its not necessary for good vaporization, but otherwise, I donīt see any tangible reason why be feared of high fuel temperatures - apart from boiling in the fuel rail which can be eliminated by high pressure.

Other points about high temperature and load on fuel pump running at high pressure. Well, fuel is heated as it cools the pump, but imagine huge fuel flow compared to heat which pump produces. Its small. Main part of heating comes from nature of return style fuel system itself. Fuel rail is the place where fuel is heated the most. Given the fact, that system operating at higher pressure is operating with less overall flow and less return flow, in-tank fuel temps could be even lower than on lower pressure system.

Just some numbers for reference

Bosch 044 at 100 psi still has 92.8% of flow at 60 psi. Current draw unfortunately isnīt on this chart, but other sources indicates about 13 A at 60 psi and 15 A at 100 psi. 15.4% more amperage - heat. Its not that bad IMO.

Only real concern is quality of the build itself

Brandon Robinson

iTrader: (3)

The response of the injector with proper dead time compensation, and at the end of the day this is the one that really matters. The coil cannot respond fast enough, yes you will lock your injector up and flood your motor.