Lowering boost to 5PSI and running 87 or 89 octane bad?

[QC DSM ESiT]

The gas mileage is so horible in my turbo minivan that I'm resorting to taking off my boost controler. The O2 sensor might be bad which is causing bad gas mileage but I can't afford another O2 sensor at the moment. So my question is, if I take off my boost controler and run it at just what the actuator is set at from the factory (which is 5PSI) and run the cheapest gasoline (usually 87 or 89 octane) in it would it hurt anything? I know you usually want to run higher octane to avoid detenation at higher PSI but since its lower PSI it shouldn't be as risky running lower octane right? Thanks in advance guys.

[turbovanman²]

Welcome to my world, lol!

Anyhow, running 5 psi and 89 octane won't hurt it at all, heck, I run 15 psi on 89 in my van right now, ;)

[moparzrule]

You can run 87 at 5-7 PSI no problem. If you are intercooled, since it's winter time I wouldn't even hesitate to run 10-12 PSI on 87. A 2.5 only has 7.8:1 compression, Honda's are running 10 PSI with 10.8:1 compression on high test. I think you will be fine ;)
Now, think about this really. 93 octane is 20 cents per gallon, what do you use 10 gallons on a fill? Thats 2 bucks man, it's gonna take a LOT of tank fulls to pay off an O2 sensor.

[turbovanman²]

You can run 87 at 5-7 PSI no problem. If you are intercooled, since it's winter time I wouldn't even hesitate to run 10-12 PSI on 87. A 2.5 only has 7.8:1 compression, Honda's are running 10 PSI with 10.8:1 compression on high test. I think you will be fine ;)
Now, think about this really. 93 octane is 20 cents per gallon, what do you use 10 gallons on a fill? Thats 2 bucks man, it's gonna take a LOT of tank fulls to pay off an O2 sensor.

YOu guys got it good, premium is almost a buck more, its friggin retarded, :mecry:

[stereo]

Wellas long as your not boosting when just driving around there's not really a point to lowering the boost. And that's not going to be enough to really beat on anything so you'd be doing it for nothing. Trust me, I do alot of driving and with the high gas prices I have found myself to become very anal about mpg. The first thing I watch when accelerating is the boost gauge to make sure I'm at 5 in. or under. That's the biggest gas saver right there. Next would be to have an NGK O2 in there. 30 some bucks from summit and worth it. I picked up almost 2 mpg switching from the bosch one. Vans are tricking though too. Mine is getting a little more than 20 mpg on the freeway. The previous owner said he could get 25, I don't know how. Took the seats out and that gave me 1 mpg more or so. What is everyone else getting in their van. Is the cheap gas, weight, and box shape of the van really enough to affect it by 10 mpg compared to my csx. Anyways, just try and stay out of boost as much as possible, even if it means holding people up and try to reduce some weight to and that will help and wont cost you any $. Oh and +1 for moparzrule on the gas prices. Not worth.

[Ondonti]

You can run 87 at 5-7 PSI no problem. If you are intercooled, since it's winter time I wouldn't even hesitate to run 10-12 PSI on 87. A 2.5 only has 7.8:1 compression, Honda's are running 10 PSI with 10.8:1 compression on high test. I think you will be fine ;)
Now, think about this really. 93 octane is 20 cents per gallon, what do you use 10 gallons on a fill? Thats 2 bucks man, it's gonna take a LOT of tank fulls to pay off an O2 sensor.

Basically skip a few unneeded drives and combine errands and you will get the $ saving much faster :P

[turbovanman²]

Basically stock engine and computer, TIII turbo, averaged 15 ish and got a best of 17 mpg. Last 8 valve with hybrid turbo, averaged 12 mpg, now averaging 14 mpg.

[Ondonti]

ewe I dont like this.
I put 91 in my 7.0:1 motor with only 5psi lol
I guess I better join the 85 octane 15psi boost club :P

[moparzrule]

You have 85 octane? Never heard so low. Once we had 86, I forget who sold it but it didn't last long. Everything is 87/89/and then we have 91/92/93 depending on what station you go to fill but the norm is 93. I have found that Sheetz 92 octane is better quality than some 93 octanes though.

[Turbodave]

When you get out west there are a lot of areas that have 85 octane for regular and 91 for premium. I noticed this in Denver, I actually had to decide whether or not to run 85 in my rental car. I don't know if there is something with the altitude that effects the octane rating or allows a car to run less octane, but it was suprising either way.

going back to the minivan fuel mileage. My 89 with a 2.5TI/Auto was usually about 15 in town and maybe 17 on the highway, it sucked because that's what my 1/2 ton pickup gets on regular gas. I noticed that the van would be in boost 100% of the time when cruising at 75mph.

My 90 van currently has a 89 2.2TII in it, but with a 5speed trans. I've noticed about 17mpg in town and 25mpg on the highway (coming back from SDAC-15 with the A/C on the whole way). The overdrive gear really helps as the van cruises at 75 all day and stays out of boost except on hills and when passing.

[minigts]

I know you guys are probably producing a LOT more horse power and there is more weight with the vans vs. my Charger , but 17MPG? I get 30 on the highway and mid to high 20's in the city driving normal, no racing though. Please tell me it's just because you guys are racing from point to point or maybe I don't get it.

[Turbodave]

The vans are heavy and unaerodynamic. Combine that with the fact that most of them have a 3speed non-overdrive automatic and the result is less than stellar fuel economy.

[TurboRon25]

When you get out west there are a lot of areas that have 85 octane for regular and 91 for premium. I noticed this in Denver, I actually had to decide whether or not to run 85 in my rental car. I don't know if there is something with the altitude that effects the octane rating or allows a car to run less octane, but it was suprising either way.
.


Out west has altitude. Thin air makes less cylinder pressure and thus needs less octane.
Think of it like boost. Compared to the thin air of Denver (5000ft), our 500ft Chicago air is like boost to a n/a engine. The more boost, the more octane you need. With less boost, thinner air, the less octane you need.

Ron

[TurboRon25]

The vans are heavy and unaerodynamic. Combine that with the fact that most of them have a 3speed non-overdrive automatic and the result is less than stellar fuel economy.

+1
I had a 520 in my 89 2.2 TII Shelby Daytona. I could get 36 on the highway, 41 once with an open downpipe following jt to the nats.
When I put a 555 back in I couldn't get more than 32 on the highway.
That is only going from a 3.85 to a 3.50 diff. with an overdrive 5th gear.
The van is stuck with a 1:1 third and whatever diff it has.
Gearing is a big deal.

Aero is a big deal too. Drag increases exponentially with speed.
100mph does not produce twice as much drag as 50mph, it's 4 x as much drag. The amount of power it takes to keep up with traffic in a van can be quite a bit more than in a car.

I think these vehicles were built when we still had a 55mph national speed limit. If you drive 55, there probably won't be huge differences.

Ron

[Dusty_Duster]

That 3-speed auto does a lot to lower fuel economy. I've got a P-body with the 3-speed auto, and I only get about 15 MPG around town.

[minigts]

+1
I had a 520 in my 89 2.2 TII Shelby Daytona. I could get 36 on the highway, 41 once with an open downpipe following jt to the nats.
When I put a 555 back in I couldn't get more than 32 on the highway.
That is only going from a 3.85 to a 3.50 diff. with an overdrive 5th gear.
The van is stuck with a 1:1 third and whatever diff it has.
Gearing is a big deal.

Aero is a big deal too. Drag increases exponentially with speed.
100mph does not produce twice as much drag as 50mph, it's 4 x as much drag. The amount of power it takes to keep up with traffic in a van can be quite a bit more than in a car.

I think these vehicles were built when we still had a 55mph national speed limit. If you drive 55, there probably won't be huge differences.

Ron

Well I'm running a stock 525 and get the numbers I mentioned above, so I wonder if mine would get better with the 568 I'm going to put in?

[QC DSM ESiT]

You can run 87 at 5-7 PSI no problem. If you are intercooled, since it's winter time I wouldn't even hesitate to run 10-12 PSI on 87. A 2.5 only has 7.8:1 compression, Honda's are running 10 PSI with 10.8:1 compression on high test. I think you will be fine ;)
Now, think about this really. 93 octane is 20 cents per gallon, what do you use 10 gallons on a fill? Thats 2 bucks man, it's gonna take a LOT of tank fulls to pay off an O2 sensor.

I dunno if the O2 sensor is even bad. I have no time to test or the right tools to test it. Also we have the 4 wire sensor so it cost quite a bit. I figured I would replace it eventually but it isn't throwing any code for it. I'm only getting about 14-15MPG in my van now so I figured replacing the O2 sensor couldn't hurt.

Anyway I'm gunna kick it down to 5PSI and run low octane for now and see if it helps any.

[turbovanman²]

Its tough pushing a tool shed thru the air. I wish I didn't have soo much traffic or I'd put a 5 speed in. Oh well, I have my Diesel van if I need fuel economy, :clap:

[stereo]

Again dude. Lowering the boost for driving around won't change anything unless your in it. You could have it set at 30 psi and you'd still get the same milage out of boost. Its a set thing.The computer is seeing your at 5in. and it will give the right amount of fuel. When you hit 5psi. it will now to give enough for that amount and so on. It does not matter unless your in boost. Your just wasting time and possible races by doing that. Just drive around and stay out of boost, get a ngk O2 from summit for $30, reduce some wait, check your tire presure, maybe a clean air filter, but lowering the boost won't change gas milage for regular driving.

[TurboRon25]

I think what he is trying to say is that he wants to run 87 for a cost savings per gallon.
So in order for his engine to not blow up on 87, he is wondering if he can just lower the boost so as not to blow it up on the 87 that he wants to run.
...That is what we are talking about isn't it?

Ron
+1 on a good O2. It will start paying for itself right away.

[Dez]

I'm running 25psi and 87. :]

[moparzrule]

Alky doesn't count. I'm running 25 PSI on 93 octane no alky

[Dusty_Duster]

Again dude. Lowering the boost for driving around won't change anything unless your in it. You could have it set at 30 psi and you'd still get the same milage out of boost. Its a set thing.The computer is seeing your at 5in. and it will give the right amount of fuel. When you hit 5psi. it will now to give enough for that amount and so on. It does not matter unless your in boost. Your just wasting time and possible races by doing that. Just drive around and stay out of boost, get a ngk O2 from summit for $30, reduce some wait, check your tire presure, maybe a clean air filter, but lowering the boost won't change gas milage for regular driving.

Yeah, but having a G-valve installed makes the turbo spool up FAST. So sometimes it's really hard to stay out of boost.