Economy and Injectors

[WetGTR]

Here is my situation....

I have Blitz 1000cc injectors in my engine (RB26) and they are single nossel type injector.

I only get 250km out of my tank, and there is hardly any difference between city and highway driving.

I was hoping that changing the injectors from a single nossel type to a twin nossel type would help my economy, what do you think?

I found out some prices:

Power Enterprise injectors 1000cc twin hole type $1400

Sard 800cc twin hole type $645

Major price difference!!!

Has anybody got any insight on the difference between injector brands?

This is more in reference to spray patterns, do some brands spray better then others?

Any information would really help me out.

Thanks guys!! (Oh, I've already tried searching and searching.....nudda)

[rs73]

Hmmm... I don't think the blame is 100% on your injector.

Sure it will flow more fuel than standard, but a 1000cc injectors should flow closely similar amount of fuel to 550 or 800cc injectors at the same engine load, rpm, boost and other parameters if tuned properly.

The only difference is the bigger capacity your injector is, the more fuel they can flow to support bigger HP. I'd say check the state of tune on ur ECU (I assume you should have an aftermarket ECU), or check that your fuel pressure regulator is functioning properly. Sounds like your car has been tuned overly rich.

[rob82]

Been trying to get spray patterns and delta angles off injector companies for ages and I cant find shit on the net about them. As far as flowing the same as a 550cc injector I dont know about that. Its abvious that the larger the injector the greater the size of the pintle, therefore more force require to drive. There is a thing called void blast off time - which is the time from when the ECU sends the signal till the time the injector actually opens, typically the larger the injector the greater the delay. Usually when we select injectors we select the smallest injector that will do the job that is required. You could try the twin hole types as they void blast off may be smaller then your current 1000cc injector - I do not know for sure.

Your real problem most likely lies with your tune - it worries me that your city and highway mileage is the same, is your closed loop fuel control working, O2 sensor? Not sure if 740cc Nismo's will get you there but I have found best control over the nismo items, if thats any bearing.

[WetGTR]

I've looked at my fuel maps on the ECU which is an Autronics. The target A/F ratios at light loads is 14.0:1. My tuner says that due to my cam size I get bad fuel economy as they are out of their effiency range...

I have also looked at my closed loop operation and this has been disabled in the ECU and I have no O2 sensor connected.

I asked my tuner about this and he say's that if your tune is perfect there is no need to go to closed loop for the A/F ratio correction which is what closed loop is all about. Wonder what this is all about?

I also noticed "open loop lean highway setting" which has been disabled.... wonder what this is?

So I've been looking at ways to get better economy via:-

1. twin hole injectors instead of single hole injectors - twin hole being better at light loads.

2. closed loop operation - which has been disabled

3. open loop lean highway - this is in the Autronics just under the closed loop operation.

Any suggestions about any of this.........

[R31Nismoid]

im using nismo 740's man, running a nice benno tune and i still got 370km's to the last tank (50odd litres)... and that wasnt taking it easy the whole time... and whats more no o2 sensor in there ATM either

if in doubt, you know who knows the answers

[WetGTR]

Thanks for that R31Nismoid, he said my cams are too big.

With 280 camshaft sizes, they don't run well at light loads.

I didn't doubt him when he said this as it made logical sense but there is no harm in trying to look for more ways of getting better effiency.

What camshaft size would you recommand?

Wish I was getting 370km out of my tank.....hmmm 370km very nice

I can't beleive benno can get 10L per 100km out of his car on the highway...... wow!!! thats around 500km out of a tank from a 500awkw car RB31.... his the man :Pimp2:

BTW he is only using baby cams, not sure of what size though

[pnblight]

i'm running 700cc sard injectors on pfc at 397rwkw and can easily get over 400km maybe closer to 500km if i stay off the throddle.(cam are only 260deg)

My guess would be 2) 3) the most likely factors in the poor fuel consumption

pete

[WetGTR]

Thats awsome pete :uh-huh:

400 - 500km out of a 397rwkw car is fantastic.

I wonder if I would cause any damage if I enable the closed loop operation & or open loop lean highway mode on the Autronics?

I'II need an O2 sensor as well....hmmm I wonder if there would be any difference?

[Sydneykid]

Big cams and lean running are not a good combination, it is far too easy to burn the exhaust valves. I have seen an RB26 cylinder head back in the machine shop 3 times for exactly that problem, they keep leaning it off via the closed loop aim table to get better fuel economy on the freeway.

It is not unusual for tuners to dissable the closed loop cruise for exactly that reason on engines with big cams. The alternative is to set the closed loop aim table a little richer than stoich (ie; closer to 14.0 than 15.0).

At 417 rwkw you may be slightly overcammed with 280's, I suspect that high lift 264's or 272's would do the job just as well. Worth talking to your tuner about those 2 options.

[pnblight]

I will say tho mine is a lightly tuned rb26 with gt2560r turbos and tomei poncams etc. Where yours sound pretty hard core with 280 cams and what turbo package?

I would be a properly install 02 sensor(s) running closed loop could only benefit the car

Worth a try with fuel prices like they are (if it worked wouldn't take long to pay for it's self)

[WetGTR]

Thanks SK!!

I'II be doing exactly that, talking to my tuner, thanks for the insight.

At least now we know why they do these type of things, like not running closed loop as such. I also noticed that my target A/F ratio at light loads are at 14.0.

Between my cams (280), the 272 or the 264's - would there be much power differences?

[WetGTR]

I will say tho mine is a lightly tuned rb26 with gt2560r turbos and tomei poncams etc. Where yours sound pretty hard core with 280 cams and what turbo package?

I would be a properly install 02 sensor(s) running closed loop could only benefit the car

Worth a try with fuel prices like they are (if it worked wouldn't take long to pay for it's self)

Your not wrong with fuel prices, crazy stuff.

Love to try, but as SK as said big cams and runnning lean can stuff your valves.

The last thing I want to do is damage something, I would only try if it was safe to do so.

BTW, I'm running a built engine, forges and the rest with a Garrett T04Z turbo

[rob82]

The richer mixtures at light loads is most likely to stop the car surging. This is where a slow speed probe should be used to determine CO and NO to determine the real combustion process. The higher the RPM the leaner you should be able to make it without surging. You could try setting your target 14.4-14.7 and see if the car cops it, but you would probably want to do this on the dyno. You could also enable the lean cruise function. Talk to your tuner he should be able to guide you.

[pnblight]

SK i think is mostly like right and your cams sound a bit big as i'm run a (combine turbos 640hp rating) where the t04z is what more like 800hp so i cant see why your gtr still wouldn't make that sort of hp with smaller cams (i'm run 260 9.15mm in/ex for 397rwkw)

can i ask what boost you run for the 417awkw?

and the lift of the cams?

cheers pete

[Sydneykid]

Thanks SK!!

I'II be doing exactly that, talking to my tuner, thanks for the insight.

At least now we know why they do these type of things, like not running closed loop as such. I also noticed that my target A/F ratio at light loads are at 14.0.

Between my cams (280), the 272 or the 264's - would there be much power differences?

Tough to say, we had an RB on the engine dyno recently with Jun 272/10.8 mm lift cams in it and it made 663 bhp using a similar sized turbo to yours. So I doubt that you would loose anything with those. You could try a 272 inlet cam with your current 280 exhaust cam, my own RB31DET will be getting that combination (Jun again with 10.8mm lift on each cam).

In regard to the 264's, we have seen 402 rwkw out of a 2.7 litre RB26 with 2530's, they were 9.7mm lift, so no clearancing or special followers required.

It really depends on what you can get your hands on and the cost. If you found the 264's limited the power too much, they are very easy to sell. The 272's are a little harder to sell but I doubt that you would need to. If you decide to go that way, your 280's should be pretty easy to sell as they are a great drag cam.

Oh, what lift are you runing currently?

[pnblight]

Interesting Sk the second units sound very similar combo to mine (as the hks 2530 are very similar to my gt2560r garrets) what sort of boost was that at ?

And is that a similar power to the first example 402rwkw = what sort bhp (i know it's abit of a guess) i had ~at the high 600's bhp

The reason i ask is i had woundered if i would pickup much hp with a larger cam setup.

cheers pete

[Sydneykid]

Interesting Sk the second units sound very similar combo to mine (as the hks 2530 are very similar to my gt2560r garrets) what sort of boost was that at ?

And is that a similar power to the first example 402rwkw = what sort bhp (i know it's abit of a guess) i had ~at the high 600's bhp

The reason i ask is i had woundered if i would pickup much hp with a larger cam setup.

cheers pete

Hi Pete, the 402 rwkw works out around 620bhp and it was at 1.5 bar'ish. That engine has a lot of good head work, ceramic coated combustion chambers, piston crowns and exhaust ports, a trick set of split dumps, 5" cat and a 4" exhaust. It was a very nice setup, I really liked it. So much so that we are getting a new road R32GTR shortly and I will most likely copy that set up on it.

For road use only the 272's can be a bit much. What sort of lift do your 264's have? Maybe higher lift would be an option, if you don't do enough track work to justify putting up with the 272's.

You must be getting pretty close to the airflow limit on the 2560's, there might not be any left to gain from the bigger cams. That was certainly the case with the 2530's, I don't hink they had 1 more horsepower in them.

[WetGTR]

Oh, what lift are you runing currently?

Not sure what lift I am running.... :confused: have to find out.

hmmmm, now have to think about cams :wizard:

[oh to dream]

great post guys, sorry if this is off topic but SK it sounds the 264 cams you are running are evidence to what you always say on these forums about boost being a measure of resistance to air flow as many people on these forums are running the same boost to your 2530s and making power in the low 300's with smaller cames and more restrictive heads. Your setup sounds very similar to that of the mines car so it is no surprise you are making huge power and are going to emulate it in your next r32GTR.

[pnblight]

Hi Pete, the 402 rwkw works out around 620bhp and it was at 1.5 bar'ish.  That engine has a lot of good head work, ceramic coated combustion chambers, piston crowns and exhaust ports, a trick set of split dumps, 5" cat and a 4" exhaust.  It was a very nice setup, I really liked it.  So much so that we are getting a new road R32GTR shortly and I will most likely copy that set up on it.

For road use only the 272's can be a bit much.  What sort of lift do your 264's have?  Maybe higher lift would be an option, if you don't do enough track work to justify putting up with the 272's.

You must be getting pretty close to the airflow limit on the 2560's, there might not be any left to gain from the bigger cams.  That was certainly the case with the 2530's, I don't hink they had 1 more horsepower in them.

Interesting mine has a std head and 260 9.15mm lift poncams and we run it up to 20psi. I still have std cooler aswell and have not setup a sealed cold air intake yet (in the process) just got Apexi pod filters with de-screened z32 afms and custom 3' hard piping intake system, with a twin 3' into 3'1/2 custom single exhaust. Nothing to special but boy does it doogy ,no lag to speak of and pulls all the way to redline and doesn't seem to fall away on the dyno even at near 8000rpm.

So i dont know like you said if there is much left in them but they havent hit the wall yet ,basically i stop tuning as the power level i reached was all i was willing to run through a std bottom end ,I might turn up the wick after i do my forged rebuild later this or may next year. But i go no further until internals are changed.

pete