Topic says it all. I'm trying to take into consideration now all the things that will make my car faster and get better mileage. The engine is a std. bore 350 with forged pistons, modified stock rods with a nodular crank, ZZ9 cam, Edelbrock TPI base(soon), TFS 23* aluminum heads, SLP siamesed runners, 58mm TB, AFPR, 30# Bosch injectors, SLP 1 3/4" headers, and a super-ram in the future. All boltons and free mods like underdrive pulleys are there. Car will have a 100-150 HP 'wet' system. I'm looking for around 25+ mpg. If not, hell, I understand this is a hot-rod, but I gotta try...I know there is a highway mode for the eprom but don't know how to do it on a extensively modded engine...the car has a electric fuel presure gauge and A/F ratio gauge to make it easier to tune and monitor engine performance. Thanks

 

gas mileage!!!! who needs that. buy a geo if you want gas mileage!!! j/k. actually, on the highway with the a/c on i can bust out 25-28 mpg with a 91 305 5 speed. however, in the city, 10-15 mpg. oh well, its a trade off thats worth it.

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91 Z28, 305 TPI, SLP cam & runners, 3.73 gears, Hedman headers, BBK 58mm TB, k&N, tach, speedo, Hurst short shifter, NICE stereo, alarm w/ window module, MSD 6A, HP Alt., Ported WORLD Heads, Ported and Port Matched Intake Manifold. 99 C5 Rims 17"s in front 18"s out back
EAT, SLEEP, BREATH CHEVY

 

my L98 corvette gets about 30-32mpg on the highway, my L98 iroc gets about 20-22mpg on the highway. im guessing its a wieght thing cause everything on the iroc is new, and the vette is all original with 95k miles

 

I get about 15 MPG in town and 21 or so on the Autobahn. Hell just today I saw a bran new Ford Explorer and the window sticker said 15 city and 19 highway!! Thats a 4.0L, with that said, my gas mileage rocks!!

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Convertible, L98, Mini-ram, ZZ9 cam, Comp Cams 1.6/1.52 steel roller rockers, Trick Flow 23* heads, K&N's with chopped airboxes, March underdive pulleys, Edelbrock ceramic coated TES, Flowmaster cat-back exhaust, Dynomax high flow converter, Accel 300+ box & coil, Taylor 409 wires, Fastchips custom chip, MAC sub frame connecters, Lakewood LCA & Adj. Panhard rod, SLP 2500 stall, 3.42 rear gears, 1LE aluminum driveshaft, white face gagues, and NOS!

 

With my mods I'm getting about 15 city and 24 highway mileage.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

 

How did you manage that?

I'm planning on getting around 25 if I can. I plan on keeping a tight quench and I'll be running all low-restriction enhaust components and TFS 23* heads. Oil pressure will be around 30 at idle and 50 under acceleration, at least that's what I'm hoping for, no high volume pump. Intake is also low-restriction and I'm going to tune the prom for highway mode once I figure out how...

I'm going to have I'm trying to decide if I want to tune the prom to run alittle lean under 2200 RPM for extended driving, or if I want to burn another prom altogether for long trips...I want to be able to take this thing to California next year, which is alittle over a day's drive for me. I'm a driving maniac, I can drive anywhere in the US (except Alaska and Hawaii obviously) in under a day and a half. I've driven from the Gulf coast to Montreal and back in 1 sitting without getting tired much, I don't know why...this is the reason I'm so interested in mileage. Maybe it's just cuz I'm sitting there but I always have been able to stay up for days at a time without sleep . I'd be happy with 16-18 in the city, but as I already know, you really can't pick and choose your mileage. I'm just wondering how much the 30# injectors are going to hurt me...not much if I have the computer programmed right I guess...

 

umm i get about 17 city and 20 highway...that is carbbed though, and yes i do know this is a tpi subject but i hope to be putting my TPI setup on in a couple of months and i also hope that that will help my milage...anyway, just thought id add my 2 cents

 

You didn't mention gears nor tranny; they matter a lot. On the highway your O2 sensor is king so you will get appropriate mileage if it can adjust injector pulse width to get the A/F ratio to 14.7:1.

My '88 Vette gets 31mph highway with 2.59 gears and 700R/4 while the '86 IROC gets about 25-28mpg highway with 3.42 gears and 700R/4. Both cars have full exhaust mods, some intake mods but stock heads and cam.


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Best Times:
60'=1.92sec, 1/4mi=14.42sec @93.99mph in 65deg temp

 

Did you buy the parts yet? The 58mm is a bit much for a 350. The latest Chevy Hi-Perf talks about a 12 second @111 350. They only have the 52mm, with the same cam. I have almost the same setup, with a touch milder cam and can get an honest 26+, on premium gas at 75-80. This is in an '87 Monte SS too. I'm hoping for a little more when I go from 3.73 to 3.23.

 

One last thing, the injectors seem too big also. They used 24#, set about 49psi. With 30#, you'll have to go so low on the pressure, the atomization will be bad. I had 24.9 Lucas', but had trouble diailng donw the pressure at WOT. I went back to stock 350(22#), and cranked the pressure up.

 

Well lemme answer these in order...the tranny is a T-56 and gears will be 3.42 or 3.73...I haven't yet decided but with the extra tall overdrive, I'm kinda wanting to use the 3.73's.

As far as the TB goes, I know I'll loose alittle torque, but future plans call for a Superram on the 350, then on a 400. I may use a 52mm TB as the 52mm TB/SLP runner combo is staying together...the reason for 30# injectors is to add for room for modification. I also failed to mention some additional mild porting and polishing of the base intake and heads are in order. I planned on having the injector pulse width lessened enough to compensate for the additional increase in fuel, so I could still run a higher pressure. I'd be happy at 48-50 psi. I considered going to a 26# injector, but I don't want to go with 24# SVO's because I've heard they have leaking problems due to differences in length...I think I'd be happy with 26# or 28#(?) injectors if I could find a decent set for a decent price. I haven't bought the TB yet...I may also move the 30# injectors over to a 400 TPI I'll be building in the future as a stronger replacement for this 'temporary' engine. The Superram will be on the 350 for the time being, and will also go on the 400...the SLP's will go back onto the 350. All told, I'm trying to get 420+ HP and 450 ft/lbs. torque N/A out of this 350...which is kinda of pushing my luck but it's something to shoot for. I expect to have alot better chances of getting there with the SR instead of the ported SLP's...

[This message has been edited by dhirocz (edited September 16, 2001).]

 

my iroc is alot worse than that. my 89 corvette with the 3.07 gears gets 30-32mpg on the highway. my 89 iroc with L98 and 2.77 gears gets at best 23mpg but usually lower. the vette is stock. the iroc has a new crate engine, and the vette is original with 95k. both with all new ecm, all engine sensors, plugs, wires, coil, etc, etc. both are 700R4's.

[This message has been edited by u r sofa king we tah did (edited September 16, 2001).]

 

If I want gas mileage, I drive the Hunder.
My best so far is 23 mpg mostly highway in the stock TA.

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86 T/A 5.0 A4 & 2.77 gear
15.62 @ 86 mph
93 Civic 1.6L
13.5 @ 100 mph

 

I don't think this comparison is really something good to base anything on. Most of the cars so far are of difference years, meaning the proms are VERY different. I get VERY good gas mileage for the way I drive my car, I haven't taken any data as far as the actual mileage though. But the PROM is the deciding factor and of course wear and the driver.. Tuning the prom is your friend. Ask Glenn, he will tell you all about 30mpg in his GTA.

Brendan

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1987 IROC-Z L98,SR,EB 6085's,LPE 219/219 Cam, Crane 1.6RR, EB TPI Base, 58mm TB, Stock T5, 30lb SVO, AFPR, K&N, EB TES, Catco Cat, 3" Borla Cat-Back, Accel cap,rotor,distro/other crap, Aluminum DS, 94 Disk Rear, Adjustable Prop Valve, Precision 3.73 Gears, Weld in Sub-Frame Connectors, Hotchkis LCA's, KYB Shocks/Struts, Poly Bushings all over the place, Moog Upper/Lower Ball joints and Tie Rods ends/Idler Arm, Big stereo, 730SD Conversion.

To see the ROC, Check out the webpage Here