RFC: DIY mini-Turbo ideas (long)

[milo9]

I have an older Toyota SUV that has a 6 cyl with EFI which is my main vehicle and for the occasional expedition use. After a year of following this forum and many mods, especially aero, I still have the problem of getting up the numerous hills and long steep grades, elevation runs from 3000 to 6000 feet in normal use. This model of engine has been successfully upgraded to Turbo with great results but way out of my price range. My biggest gas eater is getting up the hills at low vacuum and slow speed, coasting down the other side doesn't seem to make up for the waste.

I have added a DIY water misting system controlled by a relay off the EGR circuit, just to up the ability to run low octane gas with some more timing advance. The idea being that a water methanol mix is better than exhaust gas for the engine.

Idea 1: Install a battery operated leaf blower with approx a 130mph wind rating ducted into the side of the airbox. When the vacuum drops (I drive by a vacuum gauge) to 5"hg I flip a switch to turn on the blower. If this works a control circuit could be designed to control it.

Idea 2: The engine has a Smog Pump which according to Toyota only is used to prevent backfiring. I have added an LED indicator to the control circuit and it has only come on briefly on a long downhill run. I could reroute the hoses so that the low pressure high volume output goes into the air system where the intake was taken from, between the airbox and throttle body, switch the valve on as needed or leave it on all the time. Another case where this could be done by a control circuit. I don't know if I switch to a California CAT converter it will need more air pumped to it than the 49 State version?

Idea 3: The control circuit could be programmed to add air to either 1 or 2 by the vacuum dropping to a certain level, when engine goes into open-loop via monitoring an AF ratio meter, or when the TPS hits a set value. For now an on/off switch seems good enough when going up a hill.

Besides wanting feedback on if any of these ideas are worth trying does anyone think using boost just to get up a steep grade would produce better MPG than just creeping up it trying to keep the vacuum as low as possible without downshifting?

[serialk11r]

5"Hg sounds like decent engine efficiency to me :shrug: (~84 kPa manifold pressure)

[MPGranger]

Not to be a jerk, but shouldn't you try to coast up the hill, then accelerate down it?

Or is this an unavoidable uphill acceleration? I have a couple of those and would like to here what you finally do.

[orangustang]

Driving with load is a legitimate, tested, and in OP's case it seems, unavoidable method of hypermiling. It consists of doing all of your acceleration in bursts as short as possible while remaining in top gear, then coasting (preferably engine-off) for as long as possible. On long hills, the decision is made for you. If the grade is steep enough, it's all most of us can do to keep from having to downshift just to make it up the hill.

In response to OP, I have no idea how well it would work. I've toyed around with the idea as well, but never implemented anything. Leaf blowers normally draw close to 10A (I know my dad and I couldn't run two of them at the same time on a single 15A circuit, but I'm guessing at the exact values) I think at 110V which is 1.1kW of power. Not an insignificant load for your electrical system. In fact, a typical 85A alternator can't supply that much power, so you risk damaging that and drawing down your battery if you're on a really long hill. What that amounts to is a bigger or secondary alternator, in which case you might as well just install a supercharger with a switched clutch.

I assume you know you'll also have to pump more fuel in to go with the added air if it's anything significant. I also wonder how much of a restriction a leaf blower would create on your intake when it's off. I think it would be fine, but you might find that you'd have to devise some intake-switching system to keep things working right.

These are just some considerations, not meant to discourage you. To the contrary, I really want to see how this would work if you got it going right. People have marketed 'electric superchargers' before, but they generally are underpowered and provide negligible if any gains. Due to limits on electrical load, they can't just take the guts out of a leaf blower and say "here, slap this on your car and it'll go fast". It's going to take more engineering for your application than that.

[mwebb]

"Idea 2: The engine has a Smog Pump which according to Toyota only is used to prevent backfiring."

the secondary air system has a Kombi valve or
Anti back fire valve
it is designed to prevent exhaust from flowing backwards to the secondary air / Smog pump and burning it up when secondary air is not active

if the smog pump fails from water ingestion , kombi valve is bad / leaking or car is submerged under water .

secondary air
is used to heat up the cat converter , when the system is cold , extra air is pumped into the exhaust , extra fuel is added to the engine by the ECM , the fuel and air burn in the hot exhaust and heat up the cat -

secondary air never functions when engine and cat are hot

secondary air is not designed to reduce back firing and in fact it will have no effect on back firing at all when working as designed

the pump will not flow enough air at any rpm to make any difference at all , if used / modified to pressurize the intake

[niky]

For a six cylinder Toyota motor (three liter or four?), you probably need about 10 hp of electric motor to give you 5-6 psi. You can't run that off of the stock charging system.

[mort]

Originally Posted by milo9

Besides wanting feedback on if any of these ideas are worth trying does anyone think using boost just to get up a steep grade would produce better MPG than just creeping up it trying to keep the vacuum as low as possible without downshifting?

Hi milo,
First, you should downshift to keep the RPMs in the best range for your engine.
It takes lots of power to go uphill. Assume that your suv takes 20 hp to cruise on the level at 60 mph, and that about half of the power goes to RR and half to aero, also that the rolling resistance is about 2% of the weight. So 10 hp for RR. A 10% grade adds 5 times as much power as RR, so add 50 hp for the grade. It takes 3.5 times more fuel to go up that hill, like 25 mpg on the level to 7 mpg climbing. Being able to go faster up the hill will use gas faster.


You mention altitude, at 6000 ft the air pressure is down to about 80% of sea level and engine performance is reduced. Can you blow enough air into the air cleaner with your leaf blower to get that power back? Probably you can. You'll need to decide if it is worth it.
First, lets consider your leaf blower, 130 mph is about 11,000 f/m and the outlet might be 3 inches in diameter(?) So that would be about 570 cfm. If your engine is 3.5 l, (about .12 cu ft) and it's winding up to 3000 rpm, at full throttle that's 180 cfm. Even if the blower is not an efficient compressor it could help. There is a formula for figuring the power required to compress air, and that is what you need to know, one version is here. That page is a little off for this use, since we're raising a low pressure to 1 atm. But anyway it takes 2 hp to raise 180 cfm from 11.7 psi to 14.7 psi. My electric leaf blower uses 12 a at 120 v = just under 2 hp. At least it's in the ballpark.
With the usual inefficiencies you might expect to get half the improvement suggested by these numbers.

But... there is the electrical issue, can the charging system deliver 1500 extra watts? You'll need an invertor and wiring. There's the crazy plumbing for the air cleaner. When the blower is turned on it can't leak, and when it is off it shouldn't be a restriction.

To answer your last question, there is no way this will improve your mpg.

(Also to amplify what niky said, to raise the pressure by another 6 psi requires 4.5 more hp, and that's at 3000 rpm. To add that much boost at 6000 rpm would total 13 hp.)

-mort

[oil pan 4]

I say hack out that smog pump. Its a useless piece of junk and gut that catalytic converter its so old its likely partially clogged.

Gasoline engines typically dont see any improvement in fuel economy with water injection.

You might need to rig in a real turbocharger if you are having trouble with elevation and hills. Thats what I am doing.

You may want to try a cylinder head up grade, see if toyota makes a newer version of what will bolt to that block. Chevy camaro V6 guys would do this, they would switch from cast iron RWD heads to aluminum FWD car heads and intake and gain about 100hp and get the same fuel economy.

[milo9]

Thanks for the replys and comments so far. If I try a Leaf Blower it will be one of the cordless, Li-Ion Battery, models like Ryobi has on sale now. Just a remote switch patched into it to turn it on, no drain on the alternator which I will disable on hills as well. For the intake vent I would just add a hole to the air box for the blower nozzle. The Toyota has one of the old style round cans for the air cleaner with a snout going into the fender well. BTW, it is a 4.2L engine that evolved from an old Chevy tractor design, low compression, good low end torque.

FWIW, I saw a video at one time of car on a Dyno where they used a ordinary leaf blower and some gas, Nitrous?, blown into the air box, nice bump in HP.

I might give the Smog Pump a try first since that is just a re-routing of the hoses and give it a try, more rpm more air, and hope the MAF and O2 sensors compensate, maybe keep in closed loop longer when under load.

[vskid3]

On Ryobi's site, they only list the air speed of their battery operated leaf blowers. You might end up getting a lot less CFM from one of them than a 120v or gas blower. Its worth a shot if you need a leaf blower anyway, but I wouldn't buy one just for that purpose.