RB25 - What's your MPG?

[S14_BOSS]

Just creating this for the guys running an RB25 in their s-chassis! I would like to see what everyone is running and the type of MPG you are getting. Would also like to see how many miles you put on the odometer from the time you fill up to the time you're on E.



I'll start:

S14
RB25 S1
Stock ECU
ARP head studs
FMIC
HKS BoV
APEXI 1:1 HG
Stock turbo @ 10psi

I'm only seeing 200 miles before I hit E and have to fill up again. I drive like a granny and always stay out of boost. I'm thinking this is HORRIBLE.

[fliprayzin240sx]

Im on the same boat, I get 200-220 on city driving to the tank. I've managed to hit 300 miles freeway/cruising.

[S13 curtis]

Lol that is terrible I get over 300 miles to the tank in my c6 z06 and it's a 7liter V8. Something is Probly wrong because my buddy's rb def got more then 200 a tank are you running pump gas or e85

[fliprayzin240sx]

Stock RB ECU runs stupidly rich and pulls timing when it senses that you're running more boost. I'm running an untuned PFC, thats my reason for getting shitty mileage.

[rb25_s13*CHUKI]

When was the last tune up you did? change coolant sensors, change o2 sensor, plugs etc etc. Are you running a stock cat? For sure the stock ecu is killing you, your running 91 octane on a ecu that is tuned for 98 octane so its trying to compensate

[S14_BOSS]

When was the last tune up you did? change coolant sensors, change o2 sensor, plugs etc etc. Are you running a stock cat? For sure the stock ecu is killing you, your running 91 octane on a ecu that is tuned for 98 octane so its trying to compensate

Haven't changed the coolant sensors or 02 in about 2 years. Changed the plugs about 3 months ago, and yes stock cat.

I've got a NIStune ECU but not really sure if I should drop $350 for a tune if its not really going to help with gas mileage. It's the main reason for the thread.

[fliprayzin240sx]

A tune would help IF your tuner would tune your light and partial throttle, not just tune your full boost. I'd hit Steve Shadows up if you're in socal and have him do a full tune on a dyno.

[S14_BOSS]

A tune would help IF your tuner would tune your light and partial throttle, not just tune your full boost. I'd hit Steve Shadows up if you're in socal and have him do a full tune on a dyno.

Steve doesn't tune NIStune and required me to supply the program, consult cable. I've heard good things about Chris from DC Performance as he specializes in NIStune.

[Sileighty_85]

my RB25 gets about 17mpg City (i got a lead foot) if my wife drives it gets about 21mpg, and about 26-28mpg Highway

[S14_BOSS]

my RB25 gets about 17mpg City (i got a lead foot) if my wife drives it gets about 21mpg, and about 26-28mpg Highway

How many miles do you usually see on the odometer when you hit E? Also, what ECU are you running?

Thanks

[Sileighty_85]

I never went empty. but Id reset my TOD everytime I filled up and did the math. but yeah on 400 mile road trips i averaged 26ish and that was with some spirited driving.

Stock ECU. only mods are Walbro, Tomei FPR, Greddy Style intake plenum, and FMIC.

[banshee_rider909]

Leave fontana to East LA with a full tank and come back with on E..its about 55 miles from here to there and about 110 in total...so basically i get really bad mpg...also running stock ecu, walbro 255, and front mount...car sputters at 4k rpm so i can't pass 60 mph on the freeway unless i gun it all the way but if i want to cruise at 70 it will start to sputter

[fliprayzin240sx]

Sounds like its running stupid rich. Have you checked your mechanical and CAS timing? I'd also replace the ECU water temp sensor just in case. Then fresh spark plugs, fuel filter and toss a bottle of sea foam in the gas tank to clean shit out.

[AS240]

when i was on the stock turbo, i would get about 22mpg in city and roughly 30mpg on the highway. now that im running a hx35, it's easier to stay out of boost. now i get around 27mpg in the city and right around 36mpg on the highway doing 75mph. I'm on a stock ecu but i have a safc2. on part throttle, i have my afr's pulled out to 16.0-16.4.

[S14_BOSS]

when i was on the stock turbo, i would get about 22mpg in city and roughly 30mpg on the highway. now that im running a hx35, it's easier to stay out of boost. now i get around 27mpg in the city and right around 36mpg on the highway doing 75mph. I'm on a stock ecu but i have a safc2. on part throttle, i have my afr's pulled out to 16.0-16.4.

Damn! 27MPG city!! Must be nice. How many miles do you usually see to a full tank?

[banshee_rider909]

Sounds like its running stupid rich. Have you checked your mechanical and CAS timing? I'd also replace the ECU water temp sensor just in case. Then fresh spark plugs, fuel filter and toss a bottle of sea foam in the gas tank to clean shit out.


just need someone who really knows their way around RB motors...cause man i go through 50 bucks of gas every 5 days

[2.5T_/<ouki]

just need someone who really knows their way around RB motors...cause man i go through 50 bucks of gas every 5 days

Same with me man. $50 a week IF I'm lucky. Such a bust, however I don't have any sputtering issues everything runs great.

200-220 miles a tank.

RB25
Greddy IM
Aeromotive fpr
Stock turbo @ 11psi
Apexi 1.1 HG
3" Turbo elbow back
FMIC
Walbro 255

Idk if I should Keep my NIStune ECU and pay $350 for a tune/dyno or sell the NIStune ECU and pick up a SAFC and pay $150 for a tune. I ultimately want better gas mileage, not 40mpg hybrid but something that's not going to costs $200 a month just in gas....

[MrSanchez925]

keep the nistune.

SAFC's are garbage.. pretty much a bandaid tune to get you going imo.

[rb25_s13*CHUKI]

just need someone who really knows their way around RB motors...cause man i go through 50 bucks of gas every 5 days

The rb is the same as any other engine, We are telling you what to do.

It's your ecu and the engine just needs some refreshment.

Think about it your ecu is tuned for 98 octane atleast from the factory, your now running 91 octane so It's burning faster than the 98 octane so now the ecu has to compensate for the faster burned fuel. So it dumps more fuel to save it from detonation/knock all that bad stuff

Same with people running sr20 swaps

[Sileighty_85]

Think about it your ecu is tuned for 98 octane atleast from the factory, your now running 91 octane so It's burning faster than the 98 octane so now the ecu has to compensate for the faster burned fuel. So it dumps more fuel to save it from detonation/knock all that bad stuff



Slight misconception on this, Japanese Fuel and US Fuel are actually alot closer than ppl think.

What ppl dont realize is the Japan uses a Different Octane rating system than the US. Japan uses RON and the US uses AKI commonly seen on the pumps as (R+M)/2.

So roughly it translates to

92 RON = 87-88 AKI
95 RON = 90-91 AKI
98 RON = 93-94 AKI

give or take a point

[rb25_s13*CHUKI]

Slight misconception on this, Japanese Fuel and US Fuel are actually alot closer than ppl think.

What ppl dont realize is the Japan uses a Different Octane rating system than the US. Japan uses RON and the US uses AKI commonly seen on the pumps as (R+M)/2.

So roughly it translates to

92 RON = 87-88 AKI
95 RON = 90-91 AKI
98 RON = 93-94 AKI

give or take a point

This is great information right here! :hitit: Thanks for that!

[AS240]

with a lot of highway cruising, i've gotten just over 400 miles on a tank. lately i've been getting around 360 per tank though....i like hearing my holset spool :)

[2.5T_/<ouki]

So lucky! I always stay out of boost and I max see 200-220 full tank. Gotta save up to get this NIStune ECU tuned! I want 400 miles to a tank

[Huntsman2007]

So what everyone's saying is that just by tuning your ecu, you can get great mpg out of these motors in stock form? Just curious because I already have a nistune setup it's just not installed. I was planning on waiting til I put the 35r on, but if you guys are seeing such great mpg with a tune, I'd say it's more than worth the coin to get the dyno tune in. I get maybe 17-20 mpg on a fairly stock rb. Stock block, stock turbo, stock injectors, stock ecu, stock fpr, Walboro 255, front mount, down pipe, forward facing intake manifold, and spitfire coils.

[Sileighty_85]

A healthy, properly installed swap is a big thing. I'm running a stock ECU and get fairly good gas mileage.

A tune will help as well

[two40z]

If it matters I get about 150 on stock ecu 10 psi normal driving

[two40z]

Bout to tune with afc neo, wonder if it'll be better?

[Sileighty_85]

If your getting 150 miles to a tank, then you have an issue with your swap.

Electrical or timing is off. Dirty MAFS, TPS, Vac/Boost leaks

[two40z]

Its the cali traffic ha..

[vw203]

I can't believe people are saying 50 bucks a week in gas is terrible... When I drive the gtr it's 20 a day MINIMUM. Granted those 770 injectors arnt helping out much

[2.5T_/<ouki]

LOL! I'd probably be in more of a depression if I had to put $20 in each time I drove. 770 is def not ideal for daily driving, however my 370cc should be getting more than 200 miles to a tank..

[bardabe]

I can't believe people are saying 50 bucks a week in gas is terrible... When I drive the gtr it's 20 a day MINIMUM. Granted those 770 injectors arnt helping out much

haha i hear you knocking, I need to tune my car myself aready this rom tune bullshit annoys me. I'm running on 740cc injectors getting about 16mpg

[Sileighty_85]

Injector sizing doesnt matter, its all in the tune.

I have 740's in my SR (yeah 4cyl) but i get 27-29 Mpg .

[vw203]

That's good mileage! If you think 20 bucks a day was bad I was driving a 2000 range rover for a little while , great truck but at less then 10 mpg I found myself spending 350-400 a week at some points. Yea it was time for that truck to go.

[2.5T_/<ouki]

Injector sizing doesnt matter, its all in the tune.

I have 740's in my SR (yeah 4cyl) but i get 27-29 Mpg .

So when going in for the tune, i would need a "FULL TUNE" correct? Because i could care less about WOT as i drive my baby like shes a granny. I just want my tune to be gas mileage friendly. Would that be a partial throttle tuning issue?


That's good mileage! If you think 20 bucks a day was bad I was driving a 2000 range rover for a little while , great truck but at less then 10 mpg I found myself spending 350-400 a week at some points. Yea it was time for that truck to go.

MY GOD! Must be nice having a good job. Sucks being unemployed :|. I can't do shit to my car atm.

[smoked240]

I would get about 31mpg on long cruises if I stayed out of boost. Pretty much all stock but freddy intake and FMIC.

No idea what I will get now though..I'm thinking around 10-15 but that's running E85:yum:

I'll report back after my tune next month.

[!!chuy!!]

ive had my rb25 swap in my s13 for over 6 years now and have never tuned it. never had a problem and runs amazing...(besideds my stupid welded dif)
im running stock boost
fmic
3'' catback with 4'' isis blast pipes.
walbro fuelpump,
and stock downpipe.
ive filled the tank with premium and always get around 315-350 mpt depending on how i drive it. mostly highway, to go to work. but i always change the oil and plugs evry 1500 miles. keep it clean and healthy. oh and a z32 fuel filter. nothing fancy. but reliable.

[2.5T_/<ouki]

ive had my rb25 swap in my s13 for over 6 years now and have never tuned it. never had a problem and runs amazing...(besideds my stupid welded dif)
im running stock boost
fmic
3'' catback with 4'' isis blast pipes.
walbro fuelpump,
and stock downpipe.
ive filled the tank with premium and always get around 315-350 mpt depending on how i drive it. mostly highway, to go to work. but i always change the oil and plugs evry 1500 miles. keep it clean and healthy. oh and a z32 fuel filter. nothing fancy. but reliable.

I don't understand how! I aways stay out of boost, ALWAYS! My engine is healthy and clean without any boost leaks. I see 220 IFFFF I'm lucky.

Are you on the stock ECU?

[!!chuy!!]

stock ecu.

[fliprayzin240sx]

I don't understand how! I aways stay out of boost, ALWAYS! My engine is healthy and clean without any boost leaks. I see 220 IFFFF I'm lucky.

Are you on the stock ECU?

Doesnt matter if you stay out of boost. You're dumping fuel on partial throttle. I've leaned out my PFC alot on my off-boost map. Shit would be sitting at 11-12 on partial/off-boost throttle and I was getting 13 miles to a gallon. Leaned it out sections down to 15-16 AFR and my mileage is better. City mileage is okay but I've managed to hit 300 miles on a tank. Just need to tweak it somewhere and lean out certain areas some more. Still seeing certain areas at 13-14 AFR.

[2.5T_/<ouki]

Doesnt matter if you stay out of boost. You're dumping fuel on partial throttle. I've leaned out my PFC alot on my off-boost map. Shit would be sitting at 11-12 on partial/off-boost throttle and I was getting 13 miles to a gallon. Leaned it out sections down to 15-16 AFR and my mileage is better. City mileage is okay but I've managed to hit 300 miles on a tank. Just need to tweak it somewhere and lean out certain areas some more. Still seeing certain areas at 13-14 AFR.

Ahh!
Makes perfect sense now. I def need to tune this ECU.

[jamg]

Injector sizing doesnt matter, its all in the tune.

I have 740's in my SR (yeah 4cyl) but i get 27-29 Mpg .

wtf?

how?

what mods are on your SR?

i'm going with an enthalpy rom tune, will it help me get better MPG?

[Boostoff]

1994 R33 GTST Skyline running 34 mpg on stock motor, with 15psi tune, 3" no cat exhaust, intake, and inter cooler.

I am going to make a 40mpg 14psi tune once I get the forged motor setup, but on race tune, I expect 18-20 mpg at best ~22psi (highway, more like 8-13 city)

Get a programmable ECU, get a daily tune, the computer and tune will pay for itself in gas savings pretty quickly.

[Sileighty_85]

wtf?

how?

what mods are on your SR?

i'm going with an enthalpy rom tune, will it help me get better MPG?

Its fully Built, 2871R, But with stock Cams and Dyno Tuned with a Power FC

[S14_BOSS]

Good god you guys get awesome MPG! Making me want to ditch my NIStune ECU (since i can't afford a tune) and with the money i get from the ECU pickup a SAFC so i can get good gas mileage. I don't race, i don't drift, i just use this for my daily so i don't see what the problem would be with a SAFC.

[fliprayzin240sx]

Well, the problem you have is the stock ECU. The moment the stock ECU senses knock, itll pull timing and make your car run like poop.

[Piggy]

Good to see other hx35 set-ups getting awesome mpg's too. I can almost manage 400 a tank driving normal. Hell, I'd have to Try to hit boost and it's not like I want to on public roads...ever.

[dftsilvia]

i have a stock neo in my s14. fmic, exhaust, safc neo, apexi intake.
i get around 28mpg highway fully loaded with tires and tools and shit on my way to drift events. i have gotten 300 plus mile from full to near empty
city is around 20 depending how i drive.
i could prolly hit 30mpg highway if i took a road trip unloaded

[2.5T_/<ouki]

i have a stock neo in my s14. fmic, exhaust, safc neo, apexi intake.
i get around 28mpg highway fully loaded with tires and tools and shit on my way to drift events. i have gotten 300 plus mile from full to near empty
city is around 20 depending how i drive.
i could prolly hit 30mpg highway if i took a road trip unloaded

I don't understand this!
I recently just got my tune (NIStune) and i tuned for partial and WOT tuning.

We just wanted to do a test at cruising speeds/load I'm running 16.0-17.0 AFRs, however my gas mileage has NOT changed one bit. I am still getting only 200 miles to a tank of gas. 02 feedback is turned off so i know it's not a "bad" o2 sensor.

I'm on an S14 and whenever i fill up full at the station my tank only allows for 13-13.5 gallons. Also, i have NEVER seen the gas light come on my car, i usually just fill up whenever the needle hits the E.

Someone please explain to me how they are getting anywhere above 275+ MPG in their S14 w/ RB25.

[Nizmology]

thinking about E85 tune, any RB25's on E85 with great success/power?

[smoked240]

thinking about E85 tune, any RB25's on E85 with great success/power?

I just recently converted to E85 and had mine tuned back in January.Pretty much stock. Large front mount,Freddy style IM, AEM series 2, 10psi made 270hp to the wheels on a dynamic dyno, which I have heard is very forgiving..

[Nizmology]

I just recently converted to E85 and had mine tuned back in January.Pretty much stock. Large front mount,Freddy style IM, AEM series 2, 10psi made 270hp to the wheels on a dynamic dyno, which I have heard is very forgiving..

What did you switch back to 91?

[2.5T_/<ouki]

I just recently converted to E85 and had mine tuned back in January.Pretty much stock. Large front mount,Freddy style IM, AEM series 2, 10psi made 270hp to the wheels on a dynamic dyno, which I have heard is very forgiving..

Did you ever pick up the Pure Turbos replacement RB25 turbo? I'm thinking about it but haven't seen any reviews on it.


RB25 S2 (Rebuilt)
Apex 1.1 HG
Greddy IM
Stock 370cc Injectors
Z32 MAF (Blow Through)
Walbro 255 Fuel Pump
FMIC
HKS BoV
Z32 Fuel filter

AFR's pulled to 16.0-17.0 while crusing.

WHY THE FUCK am i only getting 200 Miles to a tank. So 15MPG?! I drive like a damn granny

[fliprayzin240sx]

It could still be pushing 11-12s on partial throttle as you're accelerating. Wideband might not be quick enough to see it and would register once you stay at a steady load point. I'm on the same boat as you right now. AFRs are 15-16s on cruise and partial but still seeing 210-220 to the tank, equates to about 15mpg city. Tried it with the o2 sensor on and off, think I get slightly better mileage right now with the o2 off. My issue right now is that my cold start is rich as fuck and since its cold as shit, it dumps alot of fuel on idle until the car gets up to 60-70 degrees.

[Darius]

I have 1200cc injectors running E85 and, due to my fuel tank mods, only have half of a gas tank. I still get 200 miles per "tank" which is about 17 mpg. Do you have a fuel leak? You are going through tons of fuel.

I used to get 25 mpg on my RB25 with stock turbo.

[Drift_FX]

2200cc's with E85..... at this point i think im getting gallons per mile... :( but still cheaper than race gas! :)

[2.5T_/<ouki]

It could still be pushing 11-12s on partial throttle as you're accelerating. Wideband might not be quick enough to see it and would register once you stay at a steady load point. I'm on the same boat as you right now. AFRs are 15-16s on cruise and partial but still seeing 210-220 to the tank, equates to about 15mpg city. Tried it with the o2 sensor on and off, think I get slightly better mileage right now with the o2 off. My issue right now is that my cold start is rich as fuck and since its cold as shit, it dumps alot of fuel on idle until the car gets up to 60-70 degrees.

I don't see how these people are getting like 25-27mpg! Mine does run rich as FUUUU when cold starting; Like 11-12's. I really want to get some good gas mileage out of this bad boy.

I don't think i have a fuel leak. Possibly at the o-rings where they mount to the intake manifold. Is there a good way to test this?

Thanks.

[smoked240]

What did you switch back to 91?

If you're wondering what I was running before E85, It was 91. I honestly don't think I will ever run gas again. E85 from here on out.

I have the cash to order the turbo, I'm just debating on if that's the next thing I want..I would really love a Holset setup and even found a manifold and turbo for cheap. I just don't want to redo my Ic piping and exhaust right now. If I do order a turbo it's going to be the pure turbo one. Sounds like the easiest option and would love to see what power it can put down.

Were you running a tuned ecu before the blow-through setup? I think the Mpg will be greatly affected depending on the tune. I have yet to check my mpg after E85 but its too damn cold to be driving it. The only downside to running ethanol is the cold start. You shouldn't have problems around 40..maybe even 30-20 depending. Try starting it in 0 lol. I would love to get the technology dodge has on their new Cummings where it heats the air coming in the intake, would be awesome to have in my Rb.

[Nizmology]

If you're wondering what I was running before E85, It was 91. I honestly don't think I will ever run gas again. E85 from here on out.

I have the cash to order the turbo, I'm just debating on if that's the next thing I want..I would really love a Holset setup and even found a manifold and turbo for cheap. I just don't want to redo my Ic piping and exhaust right now. If I do order a turbo it's going to be the pure turbo one. Sounds like the easiest option and would love to see what power it can put down.

Were you running a tuned ecu before the blow-through setup? I think the Mpg will be greatly affected depending on the tune. I have yet to check my mpg after E85 but its too damn cold to be driving it. The only downside to running ethanol is the cold start. You shouldn't have problems around 40..maybe even 30-20 depending. Try starting it in 0 lol. I would love to get the technology dodge has on their new Cummings where it heats the air coming in the intake, would be awesome to have in my Rb.

Oh my bad I read your previous post wrong, I thought you went BACK to 91 I was like oh... haha. I have the apexi power fc and tuned ecu and but I am still running stock psi on 91. Great thing about socal mornings are that it isn't too cold. E85 is hard to find out here in west La but there is literally a station close to where I live to make it worth it! I just need to pony up the cash for injectors, turbo, fuel rail, engine management, fuel pumps, etc. That would be a mound of cash all at once. I am not too worried about MPG as I am lucky enough to have a daily driver.

[smoked240]

Oh my bad I read your previous post wrong, I thought you went BACK to 91 I was like oh... haha. I have the apexi power fc and tuned ecu and but I am still running stock psi on 91. Great thing about socal mornings are that it isn't too cold. E85 is hard to find out here in west La but there is literally a station close to where I live to make it worth it! I just need to pony up the cash for injectors, turbo, fuel rail, engine management, fuel pumps, etc. That would be a mound of cash all at once. I am not too worried about MPG as I am lucky enough to have a daily driver.

No biggie haha. You should be fine with the temp where you are. The mpg will drop significantly, I'm not sure on how much yet. I will let you know once it warms up and the roads clear up. It all comes down to the tune. PFC could be used with E85 I would think, if you don't want to switch ecu's cause standalone get spendy. If you want a quick E85 conversion you'll just need injectors(rail to match) fuel pump and adjustable fuel pressure regulator. After that a tune and your good to go. I'm running a single walboro 255 and ID1000cc injectors and have no problem. I would love to see a little more power out of it though. With the stock turbo we are pretty limited.

[2.5T_/<ouki]

I've got an awesome tune done by Chris Jensen (NIStune) so I know the tune is not the culprit because he's pure ownage at what he does. My cruising AFRs are pretty lean to try and save gas however it's made absolutely no difference in MPG.

What gives?

Whole point I spent money on a tune was to improve my MPG.

[PrimeDirective]

I just got 20.9 MPG with mixed highway driving and some aggressive driving on some twisty roads. I was a little above E when I filled up and the pump shut off at 12.01 gallons.

I have a stock S1 RB25 with stock turbo, boost, fuel pressure, and ecu. The only 'mods' I have are 3" exhaust, fmic, Fidanza flywheel, and Greddy style intake manifold. My AFRs while cruising on the highway bounce between 14.6 and 15.1. I also run 245/40/17 on all 4 corners.

Edit: I also stopped at a weigh station on the way home and with out me in the car the front was 1500lbs and the rear was 1250lbs and I'm pretty sure it was rounding up to the nearest 50lbs. I wanted to know the balance with me in the car but the brightness on the scale LCD was so low I couldn't read it without pressing my face against the glass.

[EvilRB]

Going to this past SEMA from LA It took me a tank and a quarter to get there roughly 250 miles in each way...
so what is that 8 miles per gallon? LOL!:2c::2c:

Here my list:
Series 1 RB25DET
Apexi PFC w/ unkown / old tune
Stock injectors
Neo Turbo
3' straight pipe w/ no cat.
ARC BOV
stock side mount
boost controller set at .8 bar
and at the time, exhaust and vaccum leaks...
oh and the car comes stock w/ 4.3 gearing so on the HWY the engine sucks when your trying to curise at 80mph going to vegas with everyone else...

This is in a A31 Cefiro so the car is alittle heavier since it's a 4 door
But it was really shitty!
Can't wait for my next tune since most of these problems are sorted out and it has a bunch of new parts on her!

[fliprayzin240sx]

Fuck, my AFR finally got dialed it, I'm back on 20mpg!!!

[Sergio180sx]

Love this thread so coolent and o2 sensors are a must when doing a swap?, are neo and series 2 sensors the same?

[watkiichael6]

I get out of churchhttp://htcf.info/17.jpg
http://htcf.info/18.jpg
http://htcf.info/19.jpg
http://htcf.info/20.jpg

[redline racer510]

16city 25hwy
As long as you are around 15hg of vac you should be getting decent gas mileage.

[supersayianjim]

Love this thread so coolent and o2 sensors are a must when doing a swap?, are neo and series 2 sensors the same?


it's funny. we both have the same cars.

on my old rb setup(rb20) i got 318 miles a tank on my s13. mix highway and city. now with my rb25??? not sure yet havent ran that long.