Old Crower Mileage Kit

[KenMc]

In the late 70's or early 80's Bruce Crower developed a kit for the 350 SBC that reportedly improved mileage significantly. It used a very high compression ratio combined with late intake valve closing. The theory being less throttling losses, less compression stroke, higher expansion ratio. Does anyone have any information on this kit? Crower was no help. Thanks.

[abaird]

Interesting. But if you have shorter compression stroke(intake valve remaining open longer) what will that do for compression? Sounds kinda like a miller-cycle engine but they have less compression and use a turbo.

Maybe you could make a kit. Put some domed pistons in with some higher ratio rocker arms on the intake valves. May need to retard your valve timing too. I don't know if this would work though.

[KenMc]

I think the trial version used an off the shelf domed piston that actually projected up into a recess machined into the head in order to get the static compression ratio high enough. I assume the production kit just had a very high compression ratio custom piston. I was hoping someone had some info on how high the production compression ratio was and when they closed the intake valve. I checked with Crane and it is not too expensive to have a custom flat tappet cam ground.

[madmike21]

Hello, I built 2 engines in the 70''''s with these cams (mm-1 and mm-2) from crower and used 12 to 1 compression on 1 and 11 to 1 on the other. They idled bone stock, had great pulling power on 89 octane gas with no ping and had great acceleration while getting 18 mpg in a 3/4 ton pickup pulling a 7000 lb trailer full of concrete finishing equipment! The cams hold the intake open about halfway up the compression stroke which cuts the cylinder pressure at low speeds, but gives you the same expansion ratio as the 12 to 1 compresion at speed. The other one got 25mpg in a full size chevy blazer! Crower acts like they never existed, but Predator cams is about to grind me something similar to play with as the price of fuel makes it worth looking at again. If you still check this forum, let me know and I will keep you informed if I can make it work as before since it will be a proprietary grind this time.By the way, the intake lobe looked like a roller lobe it was so wide across the nose and the exhaust lobe looked like a STOCK FLAT TAPPET LOBE.

[MagicRat]

It's possible this 'kit' also included fast leak-down lifters. These are sometimes used with radical grind cams because they lessen the side effects of such cams (rough idel, low vacuum etc) at low speed, but give the full effect of lift and duration at high speed - like variable valve timing.

IMHO, late valve closing would only serve to shove a bit of fuel - air mix back in the intake manifold, and I have never heard of that being a good thing. Fast leak down lifters may have made such timing work better throughout the rev range.

As for Crower not acknowledging the kit, us old timers remember back in the 70's and early '80's there were many parts promoted as being good for economy that one never sees these days............ anyone remember Holley's Mile - Dial carburetor kit?

[KiwiBacon]

The atkinson cycle is quite common these days. I've heard rumours that some cars with variable valve timing can approximate the atkinson cycle but I don't know which cars.
The prius runs an atkinson cycle engine. The higher expansion ratio than compression ratio gets a little more from the expanding gas.

But there is a downside.
Because your intake valve closes later, you're trapping less air. It's effectively cutting your engines displacement which will impact on torque and power.
A smaller engine will probably get you a similar result.

[KenMc]

madmike21,
Thanks for the reply to this old post. I bought a project car about a year ago solely for the purpose of trying this. Unfortunately other comitments have prevented much work on it. I purchased the software and cables for monitoring and recalibrating the ecu, since the VE tables will need drastic revision, and that is about it. A friend did a little modeling on "Wave" by Recaro to try to help with the cam grind and compression ratio. A first trial showed some partial throttle BSFC improvements but we have not had a chance to do any refinement. Keep me posted and/or send me a PM if you have time. I am very interested. Ken

[MagicRat]

Thank you for the reply Ken.
I had not noticed the old date. Had I done so, I would have closed the thread. So I am glad you found the info useful, as it justified the oversight.

[Moppie]

I think a thread containing this sort of info, and potential for discussion we can leave open

[KenMc]

The Ford and Toyota hybrid cars claim to use an Atkinson Cycle engine. I found some cam specs but could not tell if the durations and open/close points were "advertised", 0.050" lift, 1 mm lift, or what. There may be some better info out now. If anyone has a source for this info and the CR it ouls be a big help.

[curtis73]

Originally Posted by madmike21

Hello, I built 2 engines in the 70''''s with these cams (mm-1 and mm-2) from crower and used 12 to 1 compression on 1 and 11 to 1 on the other. They idled bone stock, had great pulling power on 89 octane gas with no ping and had great acceleration while getting 18 mpg in a 3/4 ton pickup pulling a 7000 lb trailer full of concrete finishing equipment! The cams hold the intake open about halfway up the compression stroke which cuts the cylinder pressure at low speeds, but gives you the same expansion ratio as the 12 to 1 compresion at speed. The other one got 25mpg in a full size chevy blazer! Crower acts like they never existed, but Predator cams is about to grind me something similar to play with as the price of fuel makes it worth looking at again. If you still check this forum, let me know and I will keep you informed if I can make it work as before since it will be a proprietary grind this time.By the way, the intake lobe looked like a roller lobe it was so wide across the nose and the exhaust lobe looked like a STOCK FLAT TAPPET LOBE.

And I'm sure you could burn one of several fuels including paint, water, and fairy dust.

I don't think so. Holding the intake valve open that late is something even top fuel dragsters do. Doing that on a street car would kill mileage or torque depending on the LSA. The intake reversion alone would make that engine idle like a nitro dragster and if it really looked like a roller lobe it would destroy itself on a flat lifter the first time it turned over.

Grrrr.

I'll leave it open, but if I hear one muttering of the words "pogue carburetor" or "oil conspiracy" I'm shutting it down instantly. Keep it real and factual, guys.

[bobss396]

The cam was called a Mile-A-More, which might have been an RV towing cam package. I don't recall if it was a Crower or Isky offering. My bro had one in a stout 327 that had a lopey but decent idle and pulled very strong.

Bob

[KenMc]

I am not sure what it will run on but the Prius has a CR of 13.5 and holds the intake valve open between 80 and 120 degrees ABDC. See the attached link.
http://www.electrifyingtimes.com/priustechspecs.html

I assume the 120 degrees is for lower rpm and higher load whereas they close the intake a little sooner at light loads and or higher rpm.

Torque may be lousy but the economy must be good or an OEM would not be using it. The exhaust timing seems conventional.

Does anyone know the basis of the Prius's timing? (.002" lift, 1 mm lift, 0.050" lift etc. ) Thanks

[curtis73]

If that website is quoting OEM specs, usually Japanese companies list either seat-to-seat or 1mm lift. Hard to tell which.

The later intake closing would be suited to higher RPMs, which is why I find it hard to believe that a mileage cam would have such a late IVC. It would destroy low end torque which is where mileage and efficiency can be maximized.

[KiwiBacon]

Originally Posted by KenMc

I am not sure what it will run on but the Prius has a CR of 13.5 and holds the intake valve open between 80 and 120 degrees ABDC. See the attached link.
http://www.electrifyingtimes.com/priustechspecs.html

I assume the 120 degrees is for lower rpm and higher load whereas they close the intake a little sooner at light loads and or higher rpm.

Torque may be lousy but the economy must be good or an OEM would not be using it. The exhaust timing seems conventional.

Does anyone know the basis of the Prius's timing? (.002" lift, 1 mm lift, 0.050" lift etc. ) Thanks

That's the atkinson/miller principle. It effectively cuts your engines displacement, but gives you a longer expansion stroke and the resulting efficiency gain.
There are also claims that the prius does better on E85 than on normal petrol, possibly the computer is smart enough to change inlet valve timing to run a higher compression ratio too? I'm guessing here.

The prius engine is a poor performer as far as torque and power go, but efficiency it does well.
115Nm at 4200rpm (short of the 100Nm/litre benchmark).
57kw at 5000rpm (works out to 108Nm).
In comparison the 5E-FE toyota engine (their old 1.5 litre economy motor) has 130Nm at 4400rpm and 67 kw at 5400rpm.

Here's the Prius BMEP and BSFC plots. I cannot recall where I got this from, but the peak value of 230g/kwh is very impressive for anything but a diesel engine.