Opel GT Forum banner
81 - 95 of 95 Posts

·
Registered
Joined
·
2,376 Posts

·
Pedal Smasher
1973 Opel GT
Joined
·
2,805 Posts
Hmm. Article says one advantage of lasers is that they can ignite the fuel in the center of the cylinder. Doesn't a hemi do that already? Not that there aren't other benefits for lasers. Faster cycle time for one.
Nope. It still ignites from the edge. By center of the cylinder, they mean away from the edges. Not mentioned is that the design could also split the ignition point into many points. Imagine a floating spark, dead center of the combustion area when a piston is at a specific spot.
 

·
Just Some Dude in Jersey
Joined
·
15,702 Posts
Discussion Starter · #83 ·
This sounds like a really great idea. With the right kind of lense or refractor a single beam of laser light could be broken into many smaller beams and ignite the fuel all at once. Or multiple lasers in one cylinder could be programmed to fire sequentially to form the desired wave front for various combustion chambers.
 

·
Pedal Smasher
1973 Opel GT
Joined
·
2,805 Posts
Even with one ignition point, when it's at the center of the gas, that is how the research showed a 27% gain in efficiency. When this tech finally reaches production, it will be a game changer for for fuel economy. Combined with a hybrid power train, I see a very strong future for the ICE. I'd love to see the tech retrofitted to distributor ignition systems with some sort of laser plug that is a direct replacement for a spark plug. That would be awesome.
 

·
Just Some Dude in Jersey
Joined
·
15,702 Posts
Discussion Starter · #85 ·
I am now upgrading my used stock 2.4 engine to one of Charlie's 2.5L higher compression motors. I think he has refined his engine formula by having the machine shop do a little more valve un-shrouding to reduce the compression away from the danger zone where race gas might be required. I'm totally guessing that the compression will be between 9.5-10:1 and will likely require using high test gasoline. Okay, now questions:

Does anyone know what the compression on a factory stock 2.4 engine was supposed to be?

If you increase the compression on an engine, is it recommended to use a hotter or colder spark plug?

If you increase your engine's compression, should you increase or decrease your spark plug gap?


I am currently using NGK BPR 7HS spark plugs gapped to somewhere around 30-35. I just bought new ones and they are currently gapped to 28.


Is my hot/cold temp okay on these, or should I return them and get a hotter/colder variety?

What would you recommend I gap my plugs to?
 

·
Registered
Joined
·
171 Posts
If you increase the compression on an engine, is it recommended to use a hotter or co

Hi. I Have found each compression point gives about 2.5 - 3 % power increase and usually, I find if the engine is jetted correctly for street use. you may need to go colder plugs once power is up more than 15 % than standard. So compression alone is not usually cause to change the plugs. Same goes for gap. If you drive very hard or have hot cam, big carb, and extractors etc. go 2 grades colder this will cover most scenarios including quite a bit of engine mods.
 

·
Registered
Joined
·
11,747 Posts
If you increase the compression on an engine, is it recommended to use a hotter or colder spark plug?
I'm going to pick on this one.
If you're only going to putt-putt around at 35 mph...a hot plug would work.
If you're going into higher rpm's colder.
You still got that high stall(4500) converter?
 

·
Pedal Smasher
1973 Opel GT
Joined
·
2,805 Posts
The application is almost more important than the dynamic compression ratio of the engine. You could have two identical engines, one lives its life in a race car and the other lives its life in a commuter car. The two engines would likely require different spark plugs, even though everything else about the engines are the same. What changed is the overall state at which the two engines are ran. Commuter cars spend most of their time below 4,000 RPM and a racecar will spend a great deal of its life at and above 4,000 RPM.

It would be a good idea to figure out the dynamic CR of the engine when considering spark plugs and fuel requirements. Static CR is rather useless when thinking about spark plugs and fuel requirements because you don't start building compression until the valves are closed. You could have a high static CR with a rather low dynamic CR due to a long duration cam with a late closing angle, and run the engine safely on pump gas with a typical off the shelf spark plug. The opposite could be a pain in your neck. You could have a rather run of the mill static CR but due to other variables such as the cam, wind up with a high dynamic CR that results in needing race gas and cold spark plugs. A cam with high valve lift but short duration could be the most dangerous thing you installed in an engine if it resulted in an early closing angle, allowing the engine to create dangerous levels of compression. This is why blueprinting an engine can be very important, it allows you to verify key measurements and calculations so you don't blow up your engine.
 

·
Just Some Dude in Jersey
Joined
·
15,702 Posts
Discussion Starter · #90 ·
Charlie worked out the problem of the excessive compression with a switch to dished pistons, so we're thinking the compression will be closer to a more normal 9:1. He'll give details about it soon in his thread. I didn't want a racy performance engine that loped at idle or felt like it was going to stall all the time because it was so jacked up. The new piston choice should make this a fairly normal rebuild with normal compression, but with a little bit more displacement to 2.5 liters and a little bit bigger valves with a little bit lighter pistons than my stock 2.4.

No, I don't use the high stall torque converter on this car, Charlie now has that. Gil suggested that I don't use it with the 2.4. He was right, the auto tranny with stock converter works so good with the 2.4 it's friggin' amazing. You can't detect the shifts, they're instantaneous and always at the perfect time. That was far from the case when I was using 2.0's with Combo cams.

Yup, my driving style is just to putt-putt around for the most part due to all the traffic around here. I don't beat on my cars' engines, I like'em to last forever.
 

·
Über Genius
Joined
·
9,528 Posts
Charlie worked out the problem of the excessive compression with a switch to dished pistons, so we're thinking the compression will be closer to a more normal 9:1. He'll give details about it soon in his thread. I didn't want a racy performance engine that loped at idle or felt like it was going to stall all the time because it was so jacked up. The new piston choice should make this a fairly normal rebuild with normal compression, but with a little bit more displacement to 2.5 liters and a little bit bigger valves with a little bit lighter pistons than my stock 2.4.

No, I don't use the high stall torque converter on this car, Charlie now has that. Gil suggested that I don't use it with the 2.4. He was right, the auto tranny with stock converter works so good with the 2.4 it's friggin' amazing. You can't detect the shifts, they're instantaneous and always at the perfect time. That was far from the case when I was using 2.0's with Combo cams.

Yup, my driving style is just to putt-putt around for the most part due to all the traffic around here. I don't beat on my cars' engines, I like'em to last forever.
I'm not judging but I do wonder what's the point of a bigger engine with lower compression.
 

·
Just Some Dude in Jersey
Joined
·
15,702 Posts
Discussion Starter · #93 ·
A Rebuild with Benefits

All I wanted was a rebuild. If I can get a rebuild that keeps compression the same, but with a little more power and drivability for the same money, why not opt for that? There was an initial problem with the machine shop's choice of flat top pistons for Charlie's first engine or two, which caused the too high compression and the need for race gas or a cam that would lower compression and allow normal pump gas to be used. Dished piston's should fix the too high compression and the engine should operate and run like a "normal" passenger car engine.

:veryhappy
 

·
Registered
Joined
·
1,889 Posts
Any Ideas for plugs these days?
I've converted my ignition to electric pertronix 3
The plugs that are in it now are bosch platinum 4032
But I also have the newish plugs I pulled out of it which were ngk bpr6hs
Stock 1.9 8mm wires
I just want to make sure I'm making the little upgrades properly
 
81 - 95 of 95 Posts
Top