Turbo backpressure's effect on MPG

[guitaraholic]

Ok, we all know if you stomp on the gas, and are in boost, your mileage goes to hell in a hand basket. My question is this, how much does a turbo effect mileage (highway) reason I bring this up. My 240sx use to get about 32mpg with a KA, with an AUTO. Now with an SR20det (S14 w/VTC) I am lucky if I get 28 maybe 29 if I throw some octane booster and that's ALL highway. Technically the Sr w/ a manual, smaller displacement, VTC should do at least as good if not better than the KA, Thanks everyone.

[240trainee]

I think you are getting pretty damn good milage myself, there are always freaks, but 32mpg for an auto 240 is pretty damn good, my great cond vert with the top up gets 24 town/ 29 highway.

and milage isn't all about displacement.

[axiomatik]

yeah, i don't know how you are doing it, i always got 22-23 on my KA, now I get about 26 in my SR (about 60-70% HWY).

[guitaraholic]

Shoot, I once had an Eagle Talon, that I rebuilt the 4g63 in it. Only thing I did was P&P the head, headers, downpipe, (STOCK muffler and cat), rem balance shafts, and balanced everything. I got 35mpg on highway doing 80. I know there are quite a few variables to consider, but heck. the Sr20 and the 4g63 are similar in displacement/bore and stroke, and heck I think maybe even the stroke/rod ratio is even close. I did hear that upgrading to a T3 (ie 3071) would reduce backpressure, There is a guy somewhere on these forums that gets 31mpg with an SR and has 550 injectors.

[Daniel.]

Shoot, I once had an Eagle Talon, that I rebuilt the 4g63 in it. Only thing I did was P&P the head, headers, downpipe, (STOCK muffler and cat), rem balance shafts, and balanced everything. I got 35mpg on highway doing 80. I know there are quite a few variables to consider, but heck. the Sr20 and the 4g63 are similar in displacement/bore and stroke, and heck I think maybe even the stroke/rod ratio is even close. I did hear that upgrading to a T3 (ie 3071) would reduce backpressure, There is a guy somewhere on these forums that gets 31mpg with an SR and has 550 injectors.

thats damned good gas mileage. I get 15/19 in the evo. :(

[EchoOfSilence]

are you sure you're doing your math right man? hahah


that's pretty damned good

[DJ_Sunrise]

I squeezed 15mpg out of this last tank... How can you complain about anything above 25 with an SR? Jesus. You kids are lucky...

-Bart

[Pank]

displacement has little to do with mileage. gearing and power make more of a difference. You can have a tiny 1.6 liter engine, but if its in a van, its having to operate WAY outside of its efficiency range. Shit, my Previa only got like 20mpg highway, with a 2.4l 4cyl. on the other hand, a 505hp ls7 v8, with its tall ass overdrive, can give you ~26mpg on the freeway, in a z06.

[Dutchmalmiss]

yeah i learned to save way more MPG through throttle control. with daily-drive shifting, the turbo should rarely spool right? Also, i wanna assume since there are mods that improve air flow/fuel delivery/spark, then you should be able to maintain, or even improve, fuel efficiency (w/o the added spirited driving of course).

btw my mom's murano (VQ35 w/ CVT) gets about 29mpg AVG! so displacement shouldn't be a huge factor.

[EchoOfSilence]

displacement shouldn't be a huge factor when the technology behind that engine is up to date.

[shahee1]

I was getting 25 - 28mpg in my rb20det highway doing 65 - 70mph ... There are sevaral factors affecting your mileage (which is really great), such as driving pattern (Which must be conservative since you are watching mpg), condition of engine(you would not get same mileage on an ailing motor), OEM ECU setup (a bit more aggressive than KA tune) ... other areas to notce would be new gearing from motor swap (tranny/Rear) ... may reduce mileage also. As it stands I could not see you getting much better.

[Daniel.]

Pank is correct. I drive my evo on boost almost everywhere I go. On a really good tank, if it's all highway and I dont fuck around I get about...22mpg or so.

[guitaraholic]

Ok, well, I'll consider myself lucky on the mileage. Still wondering how much the turbo effects mileage. Anyone here Turbo their KA, no internal work done and notice a change in highway mileage? I know in the city it will go down. Also, would a tubular exhaust manifold act "kind of" like a header, streamlining the flow a bit, hence, less back pressure (ie slightly more H.P. and efficiency/mileage). No, I not trying to make it an economy car, hell I'm happy with the fact I get ~28mpg and can blow away V6's and some V8's. Well not a corvette yet. (that's what the NOS is for..hehe)


B.T.W. Yes the Talon (non-turbo) did get ~35mpg,, because on a trip from Oklahoma to Florida, I did over 500 miles on one tank, and its only 15.4 gallons. True, after the 500 mile mark, I looked for the first gas station, Was a bit hairy,, but was trying to see if I could do 500 on a tank. Oh, I had an UDP on it to. Forget to mention that.

[kevtrinh]

I get around 32-34 highway 75+ on a s13 SR....then again I weigh like 130lbs haha

[SexPanda]

Damn. I get about 28 around town with my KA. Ive babied the engine though, and I shift like an old lady...

But when I stomp on it on interstate 70 I can watch my gauge do the whole "George Bush's approval ratings" routine.

Basically, if you drive it like you stole it, your going to get shitty mileage. Whith prices the way they are, its prolly not a bad idea to shift at 2500, rather than 5200.

[kdashy]

When a car is turbocharged the engine is always under load.

Highway milage will definitely suffer.

[steve shadows]

I usually have gotten better car milage out of sr20s, even ones tuned with larger injectors, thank ka24e, I think the dual cam ka is more eifficent and cane get close in milage to the sr, but your number wow, good condition car

[motegineon]

i got 32mpg out of my last roadtrip...thats with sr20, 550 inj ect..

[DrEaM MaKeR]

Tuning is a big factor also.

[Slip&Sliden 240]

I get 15-17mpg in my q45. Thats my daiy, 22gal tank might last a week. 70 bucks a pop to fill the tank.

[Wei240]

my KA had 30 mpg, mostly freeway, I can't get anywhere close with the sr...
closest is around 26 mpg, mostly freeway...

[guitaraholic]

Hey motegineon, do you have the stock turbo (T25/28) or did you upgrade? I know that T3's cause less back pressure than T2's.

[KA-T_240]

last highway trip for me(built KA-T, gt32, 75lb. injectors.....) 28.7mpg in some hills with some messing around to keep awake, i do not have cruise control(which can get you better mpg, esp. when turboed do to not being like in boost if u hit a bump on the highway, LOL) I get between 16-22 in town, but I beat the crap out of my car.

[guitaraholic]

Was that about the same mileage you got before you turboed it Mach5?

[KA-T_240]

I never had my car on the highway NA. in town was right around 24 intown, and like i said. I drive my car hard.

[BustedS13]

my 240 hasn't been driven regularly in two years. but when i did, i always averaged about 22 daily driving, no matter how much i got on it or didn't. lots of city driving. i took a road trip down to gulf shores once, though, and averaged 31mpg with a full trunk and three people in the car.