Yep...... Might as well Do it Right !
Yep...... Might as well Do it Right !
STM317 said:No fuel crosses the valves in a DI engine. The deposits in a DI engine are a result of EGR and crankcase PCV systems recirculating sooty, oily mix back into the intake and not having any fuel present to clean it off.
I can't think of any modern engines with EGR. They do all that with variable cam timing now.
STM317 said:frenchyd said:wspohn said:Yeah, the DI has significant cooling effect and allows you to run more boost that yu would otherwise. I see 25 psi+ on my Ecotec.
DI also has it's own issues - carbon deposits on intake valves, and with a turbo engine you can't run any sort of cleaner through the throttle body, or it can kill the turbo bearings.
Even non DI engines can have significant boost with modern engine comtrols - an S54 BMW has 11.5 comprssion ratio and can still be turboed
I’ve given the deposits in direct injection engines some thoughts. Deposits have to come from someplace. I’ll assume that the air injected is clean, some sort of filters,ie no chunks of dirt.
Then the deposits have to be a result of fuel. Maybe fuel isn’t being directed down the intake anymore, but we all know about valve overlap. We know what cleans deposits. Alcohol!
A fuel rich in alcohol will clean deposits.
No fuel crosses the valves in a DI engine. The deposits in a DI engine are a result of EGR and crankcase PCV systems recirculating sooty, oily mix back into the intake and not having any fuel present to clean it off.
The deposit has to come from someplace. It probably happens in the moment of valve overlap a slight amount of fuel splashed up behind the valve. Think of the combustion chamber as a oil refinery. There is always oil leaking someplace, maybe in trace amounts but it’s there. To clean it off you’d need something. Alcohol is that something. Try wiping up spilled oil with alcohol, comes up really nice doesn’t it? So trace amounts of alcohol are injected with that dirty nasty tar you call gasoline and wipe up the residue.
Every car with direct injection needs a flex fuel emblem ( and ability) Problem solved. Next
As far as pistons, is the combo of compression height above the pin, pin size and bore size such that you might be able to use (possibly with some modification) a set of off-the-shelf pistons meant for a different engine? If so, that could end up being a lot cheaper than the other options.
In reply to rslifkin :
I’ve looked for something that will work spending hours with piston catalogs. The critical dimensions are close in a few cases but just far enough off that time with a well equipped machine shop in order to make them work would destroy the cost savings.
I’m not a snob, I made my own piston holder using wood and a drill press. Then clamped my pistons in and with a fly cutter cut my own valve reliefs after I’d sold my vertical mill
I can hone piston pin holes out a modest degree with another home made jig without losing critical alignment but my lathe is too sloppy to cut the relief in the center to turn a flattop piston into the dish shape I really need.
Then the final nail on the coffin is rebalancing everything. All that equipment left years ago.
What dimensions are off on the ones you've found?
In reply to rslifkin :
Too long ago to remember. Bore wasn’t hyper critical because I assumed I’ll bore the liners to whatever is available. The pin size would either be Jaguar or Chevy pin depending on if I decided to offset grind the crankshaft to gain stroke. Now I could possibly use certain Ford rods or even Honda rods, Well not really Honda, actually used NASCAR rods with only about 1000 miles on them. They sell pretty cheap!! they are used because at 1.94 pin diameter they have less bearing drag than the Chevy ones at 2.10 plus Honda rod bearings are very good.
Pin height and deck thickness are critical plus issues of ring thickness get critical . Finally weight and that eliminated a lot of them.
See what a slippery slope I’m on here?
Knurled. said:STM317 said:No fuel crosses the valves in a DI engine. The deposits in a DI engine are a result of EGR and crankcase PCV systems recirculating sooty, oily mix back into the intake and not having any fuel present to clean it off.
I can't think of any modern engines with EGR. They do all that with variable cam timing now.
You can still find EGR systems on high compression engines. Mazda's current SkyActive engines come to mind. Their upcoming HCCI SkyActive X engine uses it too. As well as Diesel engines. There are probably others that could be found with a little searching.
In reply to frenchyd :
If you end up a hair low on the total stack height, the block can always be decked a little to make things match up.
Out of curiosity, what's the bore and compression height on the stock pistons?
In reply to rslifkin :
Pretty hard to remove deck height on overhead camshaft V engines especially when the jack sprocket drives the the distributor. You wind up with all sorts of issues with the chain.
In addition the iron sleeves would need to be trimmed the exact same amount but since the sleeves are loose cannot be done at the same time.
As to pin height question which con rod will we be using? Jaguar, Chevy 6.0 or 6.120, or NASCAR Honda? Stock bore in either a 5.3 or the 6.0 is 3.543 it can however go out to 3.740 without replacing the liners and with boring the block another .100 over that if custom made liners are being used.
Stroke in the 5.3 is 2.756 and I think without checking 3.013 on the 6.0 but I’m not sure of that. Do you need me to check for you?
Who’s web site do you like using? It’s been a while but I think Jegs had the easiest to reference but Summit’s was pretty good.
On the other hand neither of them had much on Japanese or German cars which is OK because last I priced they were pretty expensive.
I usually dig through Summit's catalog before Jegs, but they're both pretty good to look through.
In reply to rslifkin :
you’d think with all those pistons and as flexible as I can be about things like bore, valve cut outs and pin diameter something should be workable.
It would if I still had my good lathe and vertical mill because then I could put a decent bowl in a flat top piston and cut valve reliefs accurate enough.
I can’t use a flat top piston. With no combustion chamber and a flat top piston there isn’t any squish to direct flame.
Actually the only non-custom piston I can use is if I put the 7.8 -1 piston from a 5.3 on a 6.0 engine. Then do flycuts for valve relief I wind up with 13.5-1 compression which is probably too much for any serious boost unless I use methanol or really great race gas.
rslifkin said:In reply to frenchyd :
The problem is, if you get the flame speed too slow, you run into the diesel problem where it costs you power by significantly limiting how high you can rev the thing.
Rethinking this, perhaps not. “Limiting how high you can rev an engine”.
Long stroke engines are limited by piston speed more than flame speed. And a slower flame speed gives the added pressure for a longer duration thus utilizing the energy more completely. Further longer stroke engines produce higher torque numbers
Now I realize that longer stroke carries a burden of higher friction. But is the friction increase any higher than the friction of higher revs to gain power?
frenchyd said:Rethinking this, perhaps not. “Limiting how high you can rev an engine”.
Long stroke engines are limited by piston speed more than flame speed. And a slower flame speed gives the added pressure for a longer duration thus utilizing the energy more completely. Further longer stroke engines produce higher torque numbers
Now I realize that longer stroke carries a burden of higher friction. But is the friction increase any higher than the friction of higher revs to gain power?
On that last point, I have no idea, but probably not. As far as too slow flame speed, that point would come when you've gotten the piston all the way down and the fuel is still burning. Realistically, you'd hit some balance of stroke vs flame speed that works with pretty much any fuel, but you'd be rev limited either due to burn time or mechanical limits with the long stroke.
In reply to rslifkin :
Like the famous Bentley of the 20’s and 30’s the Jaguar of the 50’s and 60’s was a long stroke small bore engine. As was the Offenhauser
All of those are successful race engines. By the late 60’s early 70’s bore/stroke ratios had changed under to over-square. While using essentially the same fuel with the same flame front speed.
The exception being the Offenhauser designed in the 1920’s and competitive at Indy through the 1980’s no doubt the reason for that is Indy always has used alcohol which seems to reward long strokes
With it’s relatively tiny stroke of 2.75 perhaps alcohol is wasted on a V12?
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