Increasing OHV Fuel Economy

[PROPEL]

This thread is for tips, tricks, and suggestions on how to get fantastic mileage out of 1.0-1.2L OHV engined Opels.

I think 50-60+ mpg is not out of the realm of possibilty. The 1-liter Opels have an inherent weight advantage over their CIH brethren due to lighter associated componentry throughout.

Topics may include OHV-specific modifications related to:
-5-speed conversions
-Best fuel delivery (carburetion, injection, etc.)
-Engine management and timing
-Axle swaps and ratios
-Free flow exhaust and headers for small bore Opels
-Engine and head modifications related to reducing fuel consumption

Also general items:
-Reducing driveline friction
-Aerodynamics
-Optimal wheel/tire combinations
-Additional weight savings

Let's make our Opels the envy of the hybrid crowd. Please join in this discussion!

[RallyBob]

This thread is for tips, tricks, and suggestions on how to get fantastic mileage out of 1.0-1.2L OHV engined Opels.

I think 50-60+ mpg is not out of the realm of possibilty. The 1-liter Opels have an inherent weight advantage over their CIH brethren due to lighter associated componentry throughout.

Topics may include OHV-specific modifications related to:
-5-speed conversions
-Best fuel delivery (carburetion, injection, etc.)
-Engine management and timing
-Axle swaps and ratios
-Free flow exhaust and headers for small bore Opels
-Engine and head modifications related to reducing fuel consumption

Also general items:
-Reducing driveline friction
-Aerodynamics
-Optimal wheel/tire combinations
-Additional weight savings

Let's make our Opels the envy of the hybrid crowd. Please join in this discussion!

Ideally, I think you'd just apply normal 'modern' technology to the engine to get a lot more out of it. EFI with long-runner intake for torque, cranktrigger ignition mapped for rpm and load, substantially higher compression ratio (compression improves HP, torque, and mileage...the only down side is the need for higher octane), tuned header and exhaust, perhaps some light head work to improve efficiency. Use of synthetic oils helps for sure.

Assuming a GT, put on some 165/80-13 Michelins, pump them up to 45 psi, use high offset wheels to flush them out with the wheelwells with some Moon-style hubcaps, lower the car front and rear, with a slight rake towards the front. Add a front airdam, sleeker side mirror(s), swap out the 4.11 axle for a Kadett 3.89 ratio. You'd definitely give some hybrids a run for their money.

[PROPEL]

That's the direction I'm hoping for, Bob. Thanks!

For U.S. OHV owners, there's less resources available for 1.1L EFI, 5-spds, cam and engine parts, etc.

In a way, I'm hoping to establish a knowledge database for these engines similar to what's available on this site for CIH drivetrains.

So using your input as an example, when trying to build a high mpg Opel, the recipe starts with a 1.1 SR engine (for its higher compression) and 3.89 gears. What piston/stroke mods might people have done to replicate the SR? What other lightweight axle swaps to mate up to the drivetrain?

Anybody find an off-the-shelf header source or build their own successful tuned exhaust system specifically for these engines?

Can carburetion come close to what EFI would achieve? (Twin solex pdsi vs. single vs. dcoe perhaps). Or, I'm thinking, maybe a DCOE-type throttle body used on a 1.1L ssd manifold. How hard to adapt Megasquirt to the 1.1L?

I have a parts 1.1L GT to use as a test bed. Stripped of non-essential items (exposed headlamps like the diesel Rekordwagon?), it would be quite light and streamlined.

[GTJIM]

I have a 1.1SR Kadett Rallye and am going down the "economy" path with it too.
First thing to change is those Solex carbs! They are made and jetted for POWER not economy. I have a Vauxhall Viva 1.5" Stromberg CD carb and manifold to adapt. The other necessity is a Petronix ignition module.
THe exhaust system is already pretty good with an exhaust manifold that has quite long runners and is configured in a good "street" Tri-Y system.
The narrow 155 80 X 13 tyres offer low rolling resistance and a modern set of Conti, Michelin or Pirelli "Eco" tyres with their designed in lower rolling resistance should help too. 50 mpg anyone??

[PROPEL]

Awesome. Any thoughts on replacing the tranny with a 5-spd, Jim?

[GTJIM]

I have considered a Chevette or Toyota Corolla 5-speed but have done no further investigation - got to finish my GT restoration first!

[Opelkurt]

Ideally, I think you'd just apply normal 'modern' technology to the engine to get a lot more out of it. EFI with long-runner intake for torque, cranktrigger ignition mapped for rpm and load, substantially higher compression ratio (compression improves HP, torque, and mileage...the only down side is the need for higher octane),...

Regarding compression ratio; I would think a slight shave of the 1.0-1.2 head would be a simple way to slightly increase compression as there would be no subsequent effect on valve timing, as opposed to the CIH engine. A change in rocker geometry could be avoided by shortening the pushrods equal to the head shave...

Does anyone know how much, if any, can be safely shaved from the pushrod head, and what might be gained? I have both of the 1.1 versions; that is, the SR version already has a higher compression ratio than the S version...

-Kurt

[opelgt73]

Ideally, I think you'd just apply normal 'modern' technology to the engine to get a lot more out of it. EFI with long-runner intake for torque, cranktrigger ignition mapped for rpm and load, substantially higher compression ratio (compression improves HP, torque, and mileage...the only down side is the need for higher octane), tuned header and exhaust, perhaps some light head work to improve efficiency. Use of synthetic oils helps for sure.

Assuming a GT, put on some 165/80-13 Michelins, pump them up to 45 psi, use high offset wheels to flush them out with the wheelwells with some Moon-style hubcaps, lower the car front and rear, with a slight rake towards the front. Add a front airdam, sleeker side mirror(s), swap out the 4.11 axle for a Kadett 3.89 ratio. You'd definitely give some hybrids a run for their money.

Alright Bob, well I am on my way to producing a high MPG 1.1L

I am going to convert a 1.9L GT to 1.1L

Here is what I have so far:

-1.1L motor/trans from GT
-Kadett 3.89 rear axle
-2 heads (one to practice porting)
-Two intake manifolds both for using one carb (for intake template)

What I still need:

-Mega Squirt system
-Fabricate intake runners
-throttle bodies (possibly from Bike, but most likely from a Toyota)
-Injectors (with high enough pressure and ability to cover two clyinders)
-Electric Fuel pump
-programmable ignition (need to find what will work still)
-1.1L GT front leaf spring
-1.1L Radiator and shroud. Though I may just go with a custom one.

Now my plan is to use a Megasquirt FI management system. Most likely with two intake runners and two throttle bodies. However what I don't know is how to set up the injectors. In the 1.9L injection system there are four runners and four pistons. However on the 1.1L there are two runners and four pistons. So would it be possible to use one injector per runner and have it squirt twice as often?

Also in regards to raising the compression. I would like to stay on unleaded, how high of compression can I run before I need to switch to high octane?

[73Manta72gt]

I'm very interested in this thread. I just bought a 1.1GT to see how much MPG I could get with one...I heard stock ones could get 50mpg I'm planning on removing as much weight as possible since this car's body isn't really worth restoring and staying with the twin carbs.

[oldopelguy]

What I still need:

-Mega Squirt system
-Fabricate intake runners
-throttle bodies (possibly from Bike, but most likely from a Toyota)
-Injectors (with high enough pressure and ability to cover two clyinders)
-Electric Fuel pump
-programmable ignition (need to find what will work still)
-1.1L GT front leaf spring
-1.1L Radiator and shroud. Though I may just go with a custom one.

You might want to consider a TBI set-up on the OHV motor. Since the cylinders are paired unevenly anyway, a single throat would feel smoother pulses. You could also then use the TBI injection, complete, from a Sprint/Metro, as the have a fuel-only stand-alone unit that was only installed here in the US. (In Japan they still ran carbs well into the 90's.) That's the route I'm planning on taking anyway.

As to the rad, there's no reason you can't run the 1.9 rad with the 1.1, just call it a heavy duty unit. For a little more room the tiny aluminum one from a 92-ish Honda Civic would be a good choice as well. The early Kadetts had a very simple steel shroud that you could certainly mount to the bigger rad with simple welded-on tabs as well.

[PROPEL]

You might want to consider a TBI set-up on the OHV motor.

I could see one of these (2900 series) on a 1.1L sidedraft manifold.

[opelgt73]

I could see one of these (2900 series) on a 1.1L sidedraft manifold.

Thats an interesting idea, but wouldn't you still face the problem of one throttle body being shared by two pistons? In that case don't you also need to set up the injector to fire for each of the two cylinders?

[73Manta72gt]

My 1.1 GT is on the road now. I got 36.7 MPG on my first road test. What mileage numbers are others getting with the 1.1L? If I go to the pertronix ignition could how much would the MPG increase?

[73Manta72gt]

I replaced the old distributor with a rebuilt one from ebay.... 243mi/5.6g = 43.4mpg about 80% interstate highway driving.