ice95z

iTrader: (10)

So from what Im reading If I leave more room in the chamber, IE 45 quench vs 35, its less efficient N/A. If im adding a 150 shot to it, I should leave the chamber bigger and compensate for that in the tune? Wouldnt having a more efficient burn with a tighter quench allow me to run more timing than normal when on nitrous. IE retarding 2 degrees vs 4?

I understand the concept of leaving more room for error with components that cant be adjusted after the engine build, with variables that can after the fact like the tune. But how? What would you change in the tune? Would you lean it out more? How will you adjust the A/F to make up for the lost efficiency and power?

Im all for learning new things. But I always want to know how. If Im going to go with a stock size headgasket and give up power I want to know how im going to get it back? Its a purpose built n/a motor with a little spray. Not a purpose built nitrous engine. Thanks again for all the feedback replies. The only way I learn is to ask.

Sales@Tick

iTrader: (3)

If you're only spraying a 150 shot then treat it solely like a N/A engine. What me and Ed were referring to were large amounts of nitrous as in 300+ hp worth of jet. Having a more efficient burn in the chamber would make you need to run less timing not more. Having a less efficient chamber would allow more timing to be put into it.

The main reason guys running that much nitrous leave the chamber inefficient is because they are cramming so much nitrous down the throat of their engines that a lot of times they end up in the single digits as far as timing advance is concerned. If they try to lean on it just a little bit and add a degree here or there they end up making ash trays out of their engines. I was just throwing that bit of information regarding those engines into my response so that anyone else reading this wouldn't think "hey I can run a tight quench like a N/A motor and then spray 500hp worth of nitrous on top of it and I'll be good to go".

To adjust for the lost power from the more inefficient chamber you would simply add nitrous jet! It's that simple. You would run whatever AFR and timing the plug and time slips told you to run.

LIL SS

iTrader: (9)

Martin,

I'll be putting my 418 back together (well, after I officially take it apart) and your thoughts on quench are making me think about doing things a bit differently. I never thought about lessening efficiency to gain resolution in timing so to speak.

Motor was 12.9-1cr with a stock thickness gasket. Pistons are out of the hole .007-.010 (I need to double check as my brain only has limited amounts of storage) chambers are 58cc if memory serves. I was planing on putting it back together with a .040 which would make my quench quite tight .030-.033. I was originally going to do it this way to raise compression to 13.4 (Trying to go 9.9x on motor and well, who knows on the bottle). But I have always wondered about quench, not specifically to N20, but the fuel I run.

I was running a blend of E85 and 91 to come up with E48. Moving forward with the added compression I was going to run straight E85. But this isn't just an NA motor. It has a 2 stage kit where I will eventually be spraying 300-400 worth on N20 through it. The N20 is wet and will be E85 as well (I have a single Weldon 2035 pump).

Interestingly enough, at 12.9cr on both E48 and E85, the motor responded best to 26* total timing at WOT. Perhaps it was low (so to speak) due to a possibly tight quench for E48/E85 (seems lots of people preach putting more timing in for E85 than gas due to the way the fuel burns). It kind of makes sense as to why it might not have wanted a lot of timing.

So, let's think here.

To create the same amount of energy with E85, I need to put more in the chamber by volume. Doing so takes up more space (roughly 30% by volume on the fuel side of things). All things being equal, does E85 now require the added chamber volume, or larger quench area to keep the same timing as gasoline (hope that made sense)?

From what I understand E85's flame travels slower (so people say, but I have seen no real world analysis done to prove either way). Same quench volume, 2 different fuels.. If the quench is right for gas, is it now overly efficient for E85 due to the added fuel volume, requiring less timing? Only way I can justify the low timing on my combo.

I am tempted to stick with a stock thickness gasket and have the heads milled a bit more to get my compression up. Seems like the better solution.


Now I know this one is off topic for quench, but I have also been thinking about exhaust duration for E85. Since exhaust is pressurized, it requires time more so than lift to leave the cyl (Vizard does a much better job explaining it than I do).
What does the spent fuel volume look like for E85?
Is there now more gasses by volume to get rid of E85 vs gas?
Would E85 vehicles benifit from a larger exhaust to intake duration?
Put N20 on top of it. Could an N20 E85 motor benifit from some crazy split bias like 15-20*?

Sales@Tick

iTrader: (3)

I honestly have no first hand experience tuning E85. I honestly do not know what it takes as far as timing, nitrous or quench. I have a pretty vast knowledge of tuning with gas (no where near what a guy like Ed has) and I know what you can and can't do, and what you can get away with on gasoline, but E85 is something a guy like Ed would be better fit to tell you as far as quench and timing is concerned.

As far as milling versus the thinner head gasket, I'd mill personally instead of the thinner gasket.

Now one thing I do have experience with as far as E85 is concerned is camshafts. I subscribe to using more exhaust duration with E85 yes. Even more so with nitrous and even more so with the heads you have. Now I don't go crazy with the split just because it has LS3 heads. I hate speaking in general terms, but I normally use between 8-14* split on LS3 heads N/A.

Now that said in terms of exhaust volume, if we subscribe to that theory, then in theory(god I hate talking like this lol I like definite answers) the squish volume should be increased! That is just theory, but it makes sense to me!

Remember our cam conversation from a few months ago? My recommendation still stands

edcmat-l1

iTrader: (10)

E85 (alcohol in general) has a slower burn rate. It actually requires more timing to make power.

Because it also has a much higher resistance to detonation (higher octane) you have somewhat of a "cushion" when it comes to something like a very efficient chamber.

Moral of the story, if you intend to run E85 all the time, don't worry about trying to slow down the chamber any.

LIL SS

iTrader: (9)

Martin, we have to start with a theory, try it, if it doesn't do what we want or thought it would, we come up with a theory as to why and a new theory of how to make it work right and try again. Love the circle..


Ed, so are you saying to leave the heads at the 58cc and run the .040 gasket creating .030-.033 quench vs milling the heads some and running the .053 gasket at .043-.046 quench?

I would like to get your thoughts as to why my motor in it's current state made no more power 26 to 28 to 30 timing. I also tried running it richer/leaner with the higher timing. It made no more power with higher timing. It did however pick up from 22 to 24 to 26.

Sales@Tick

iTrader: (3)

I have a thought as to why, and that is the tighter quench didn't need any more timing to start the burn earlier to try and get a more complete burn because the tighter quench was in and of itself doing the same thing by making the burn that you were starting later with less timing just as efficient as starting it sooner with a looser quench.

I would personally run the stock thickness head gasket if you plan on spraying that much nitrous later on.

edcmat-l1

iTrader: (10)

It's pretty simple. That's what the parts combo wanted. Adding timing does not automatically equal increasing power. Doesn't work that. You're trying to create peak cylinder pressure at just the right time. Approximately 15 degrees AFTER TDC. If you create peak cylinder pressure too soon, you can lose power, or worse, create detonation. Too late and you leave power on the table.

Same with A/F. "Lean is mean" but it doesn't always mean the leaner you run the more power you make. For the most part, yes, but each combo has it's "happy spot" where running them any leaner won't make power, or worse. A/F is always a compromise. It needs to be considered that too.

Sales@Tick

iTrader: (3)

Did you mean before TDC Ed?

edcmat-l1

iTrader: (10)

Nope. You're trying to make peak cylinder pressure at approximately 15 degrees AFTER TDC. The fuel, combustion chamber, etc. dictates how much ignition lead is needed to make peak cylinder pressure occur at 15 degrees ATDC.

Sales@Tick

iTrader: (3)

That makes sense to me. You're trying to find the sweet spot to where you're not losing any FPS on your piston velocity after the combustion event has occured when the piston has to cycle through 3 more strokes of valve events using that energy generated from when the combustion event took place so that no piston velocity is lost until it ends up back on the compression stroke again. To little timing advance and you lose power by losing piston velocity. That velocity from the piston is what drives the rod and crank which in turn drives everything else. Too much timing and you fight the natural up and down movement of the piston by wasting energy you still had from the last combustion event and starting it too soon which will also lose power, even further advanced and you detonate. This is also why cars will stop picking up from adding timing as you've passed that sweet spot and are now fighting the up and down movement of the piston. As you said you're trying to find the perfect spot where you don't lose any power from too much or too little timing.

Too little or too much timing shows up as heat in the plug. Too much timing advance creates excess heat which is absorbed by everything in the cylinder including the piston, valves, cylinder head, cylinder walls and the plug. That sweet spot is best found by reading the plugs because they will tell you exactly when you've got the perfect amount of heat being absorbed by the plug which will coincide with the perfect amount of energy needed to drive that piston through those remaining 3 strokes without losing any energy from that last combustion event.

I get it!

Killer5.3

iTrader: (1)

The way I have always understood it Martin is what Ed said. Also it will beat the bearings up eventually if it doesn't hurt something else first. I feel that most stock bottom end failures on nitrous is from too much timing lead and it keeps beating on the piston like you said eventually beating the bearings, breaking rod bolts, rods, etc. A little conservative on timing and you lose some power, too aggressive and you tear stuff up. We have always had good luck with our stuff going by the 2-2.5 degrees per 50 rule and then putting it back in based on what the engine wants.

Sales@Tick

iTrader: (3)

Very very true. For some reason I was thinking cylinder pressure before the spark is lit which happens btdc instead of cylinder pressure atdc which is a by product of the combustion event.

ice95z

iTrader: (10)

Great info! So from what I read tight quench, the right timing events creates more velocity in the chamber and even has a cooling effect in the chamber. (Squish). The less resistance the piston has on the compression stroke, the faster it will travel, thus when cramming all that air so quickly into a tight chamber will create velocity as it exits the chamber thus giving the added "cooling" effect and making more efficient power. The 2* rule per 50 shot of nitrous makes sense due to the faster burn rate that it creates in the cylinder. I'm pretty sure I understand. I also understand why Martin would not recommend such tight chamber with larger shots of juice. Your right I can see a potential ashtray with such tight clearances and too much pressure. Thanks for the knowledge Ed and Martin. You guys are great.

SS10Tech

I would like to add a few things that have not been mentioned so far. It is extremely important to pay close attention to the materials of the block and piston as well as what rings are being used simply due to the results of piston rock when talking about optimizing quench and the squish effect. Normally a 0.050 quench is considered optimal. 0.040 was Smokey Yunick's preferred value and i have seen guys on yellowbullet go as tight as 0.028 with big block/large bore builds. All pistons tend to rock slightly as they transition through TDC and this rocking motion reduces the piston-to-head clearance which directly effects quench stability aiming for the best squish effect. Smaller-diameter pistons with tight piston-to-wall clearances don’t rock nearly as much in the cylinder bore compared to larger-bore pistons with wider piston-to-wall clearances.

As for Martin's original statement he is correct. Pockets of lean and rich mixtures within the cylinder cost power and as a result the combustion process will not be as smooth. Excessively lean or rich pockets within the chamber directly affect the rate of combustion and the amount of pressure applied to the piston thus requiring ignition timing to be used in order to dictate combustion efficiency/to optimize power.

NOS327

iTrader: (30)

Glad I found this thread.. I was looking at a Wiseco 4" rotating assembly with 6.125 rod and 1.110 pin height (9.235 assembled height), it's one of their common catalog deals. Assuming my LS3 block doesn't need decked (9.240 deck), I would be .005 in the hole. Lot of local/regional guys tell me to just buy the multi layer OEM LS9 gasket (cheap and reliable), which is .051 compressed thickness (right?). Makes .056 quench. Seems like too much...

Street/strip build, 200hp n2o, never more. With tentative head and cam selection DCR ends up around 8.2, which should be kosher n/a on 91 octane, always add 110 for nitrous duty.

Close friend squawked at it, said spend money on thinner gaskets to get quench down in .040s, as quench should improve detonation resistance more than the slightly increased compression would negatively affect it.

Thoughts?

ice95z

iTrader: (10)

.056 is high. Bring it down into the low 40's. I would get a .040 gasket and have a quench of .045. Low enough to be efficient and help with detonation but still high enough for the 200 shot IMHO.

Sales@Tick

iTrader: (3)

I agree .040" gasket and let it eat. That much nitrous treat it like a N/A motor.

bww3588

iTrader: (49)

Never assume, always measure. Your ls3 block could be at 9.235 and you end up .010 out of the hole.

Zfan

I have always run .036-.040 quench, no need for more.