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Forced Induction

Talyn, you just used the word "equate" (meaning equal to, or "=" ) and I don't think anyone ever said that. You said that DCR did not affect efficiency, I disagreed, then we both agreed. Post #27. The cam examples don't help because what you are doing with that is holding the DCR constant and changing several other things that also affect efficiency, then holding it up as an example that DCR doesn't affect efficiency. Either you can't do that or you should work for big tobacco, lol. Seriously though, you can't do that. :)
I'm confused by your example as well because you were using it as an efficiency example but compared their power curves instead.
 
I re-read the posts and looked at the calculator some more and realized the dynamic compression ratio does not change. I then asked the owner of the site to explain what the "Dynamic Boost Compression Ratio" represents. The actual line reads:
"Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 7.5 PSI is 12.81 :1." I'll post any reply.

Jayzus! Most of it is right in front of me. The dynamic boost pressure, according to the calc, is a reflection of the SCR, the valve event timing, and then squashing 151% atm in it...so yeah, unless I'm still missing something, the dynamic boost compression ratio is the NA equivalent of the turboed cylinder pressure. This is good to know when avoiding detonation. It does not change the physical DCR of the engine, however.

Correct?
 
Talyn, you just used the word "equate" (meaning equal to, or "=" ) and I don't think anyone ever said that. You said that DCR did not affect efficiency, I disagreed, then we both agreed. Post #27. The cam examples don't help because what you are doing with that is holding the DCR constant and changing several other things that also affect efficiency, then holding it up as an example that DCR doesn't affect efficiency.
Ok, I chose the wrong word. And you can't change just the DCR w/o changing other cam events. You can't just move the IVC without either decreasing the duration or moving the IVO, e.g. changing the camshaft.

I re-read the posts and looked at the calculator some more and realized the dynamic compression ratio does not change.
While I didn't come out and say "it doesn't change dynamically", i though it was clear that it didn't change unless the cam moved or changed. Its name is misleading. It isn't really "dynamic" as in changing constantly while the engine is in motion. It really shouldn't even be called dynamic because it is still fixed by the cam timing. If there was a VVT system in place it could truly be considered dynamic. If you want to really get down to the details then I suppose it could be considered (slightly) dynamic, if you take into account timing chain unloading, loading and stretch, camshaft twist, crank twist, etc.
 
While I didn't come out and say "it doesn't change dynamically", i though it was clear that it didn't change unless the cam moved or changed. Its name is misleading. It isn't really "dynamic" as in changing constantly while the engine is in motion. It really shouldn't even be called dynamic because it is still fixed by the cam timing. If there was a VVT system in place it could truly be considered dynamic. If you want to really get down to the details then I suppose it could be considered (slightly) dynamic, if you take into account timing chain unloading, loading and stretch, camshaft twist, crank twist, etc.

This is agreed, yes. In fact when I was confused about the calculator I didn't realize there were two lines, one says DCR, the other says DBCR...which I initially took as the DCR. I wasn't referring to anything you or I said...just my own skipping of an important detail, realizing it, and correcting myself. :)

The name is misleading for sure. I understand that the "dynamic" is referring to the fact that it is being calculated while engine components are dynamic. The ratio itself is not dynamic, however...except for the tiniest variations OR some sort of VVT, as you and others have previously mentioned.

Excellent! I think that's covered. Any other areas of interest? I have recently realized that when supercharging you need to cool the air in FRONT of the intake to get a denser charge and not the charge air...unless you are just doing it to help with detonation. I used to think that you should intercool everything, lol. Not so!
 
John from Wallace Racing (the site with the calculator previously discussed) wrote me back. This is what he said:


Hi, Chad.

I changed the wording on that page.
(effective probably makes better sense)

It is essentially the effective compression ratio from the addition of the boost pressure.
The additional boost pressure (at boost, usually none at idle) along with the static cr make the engine act like it has higher compression ratio.

The effective cr is at the boosted pressure inputted into the calculator.

The 'compression ratio' could be used to figure out what octane of gas to use.

If the effective cr is too high (at boost) it will probably detonate.
So, one could lower the boost or lower the static cr to be able to use the octane of your gas.

Usually one can get more power from a lower static cr and raising the boost.
(can cram more air in from the boost than from the static cr)

Hopes this helps.
(if not write back and let me know)

John Wallace
Pontiac Power Rules !!!
www.wallaceracing.com





Not that this is a big deal or anything, but I'm hardly ever right. It sure feels good to figure something out and get it right the first time. I hope this is the beginning of a trend, lol!
 
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If the effective cr is too high (at boost) it will probably detonate.
So, one could lower the boost or lower the static cr to be able to use the octane of your gas.
At what Effective/boost compression ratio does pump gas not work to combat detonation? From my own experience I had a stroker with a SCR of 8.4:1 and I needed premium. Mine currently has a SCR of 7.93:1 and I can run midgrade.
Usually one can get more power from a lower static cr and raising the boost. (can cram more air in from the boost than from the static cr)
Lowering the SCR will have a negative effective on off boost performance, so it is a trade off.
 
Well that's the million dollar question. Too many variables (like charge air temp or a/f mixture or ignition timing) to just equate a specific CR to a detonation condition. :)
 
I am so glad this thread is doing it's job. There is a ton of information out there and if we can get our grimy little paws on it, the opportunity for success is better assured.

Discussions to be had.

Child9. Yup, there really isn't, to the best of my knowledge/experience, any specific CR you can point to and say "See, it detonates, told you so...".

You can add Forced Induction to about (turbo lawn mower?) anything. What gets limited is the maximum boost level. At some point, the head gasket will give up. Along with the possibility of either the pistons or the rods quitting. I have seen all of the above.

Embarrassing that is...

A contributing factor that usually gets left out but is one of my main concerns is altitude. In particular, what we are talking what is called Mean Air Density. A can of worms waiting to be opened. MAD is so critical for Dragsters that they adjust the timing and fuel between runs to reflect the current conditions.

One of the best engines I have been involved with was the Ford flat head V8. With a 6.8:1 CCR (Mercury version, the "high compression" engine) we were able to drop 18 pounds of boost into it. Using a Roots Compressor and two four bbl carbs, we had the distributor modified to vacuum advance/pressure retard operation. We modified the block and the heads to accept a copper o-ring to seal the compression. It was the best that could be done then. Then being 1959...

Today, we have exact control over both the mixture and the timing. I use an AEM F/IC8. Easy to program, works. But, it is a piggy back and I would like to swap it out for a better controller. Not saying it is the best, just that it works as advertised.

My recommendation for tuning the timing is that a knock sensor be installed. The engine will be detonating long before you can hear it. In my case, I can't hear it at all. The frequency lies, more or less, dead in the middle of the frequency range where I am essentially deaf...

Which is why I installed a Phormula knock sensor. Now, what I installed is not what they recommend for tuning purposes. Their recommendation calls for head phone usage which, in my case, is no help at all...

As an aside here...
I spoke with AEM yesterday (7-30-13) morning about the new Infinity EMS system which has waterproof connectors so is suitable for under hood installations. Their plan is to release these as the Tuning Wizards are created. It will be a matter of time until they get to us. Keep in mind that the Viper uses essentially the same hardware. The connectors at the PCM are identical.

Right now, it is available in 8, 10 and 12 cylinder versions. The 4 and 6 cylinder versions are in development. They are also looking to "close the loop" and make it as self tuning as our PCMs are now.

Interesting.

Not Cheap. In fact, probably more than some have paid for the entire Jeep. But, that is the way it is when you chase power. It is a Hobby, not an Investment.
 
At some point, the head gasket will give up. Along with the possibility of either the pistons or the rods quitting. I have seen all of the above.
The 4.0L rods are said to be able to handle 400hp. Of course, that is with a good tune, which helps any parts live. Besides piston, detonation can nearly damage anything in the engine. Bearings, valves, valve guides, etc.
Right now, it is available in 8, 10 and 12 cylinder versions. The 4 and 6 cylinder versions are in development. They are also looking to "close the loop" and make it as self tuning as our PCMs are now.
That does sound interesting.

^^What he said. I installed the sensor (now all removed) into the block forward of the engine mount. Not many places to fit the thing as it turns out.
Why removed it?
 
You didn't. There is a ignition capacitor on the stud on the head in front of the dipstick. Many people confuse that with a knock sensor. http://www.jeep4x4center.com/ignition-capacitor.html The Renix engine has a knock sensor, but the next engine to have knock sensors was the 4.7L in the WJs.
 
Well...alright. I never touched it, that's for sure. I no longer presume that any engine has a knock sensor. A little embarrassing really, since I had one for 6 years or so. Ha.

Too bad installing a Renix sensor isn't easier. I would hope to find a cast boss or something already on the block. Oh well.
 
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Too bad installing a Renix sensor isn't easier. I would hope to find a cast boss or something already on the block. Oh well.
I believe there is a cast boss on the driver's side of the block under the exhaust manifold for a knock sensor.
 
^^Yup, there is. That is where I had mounted mine. It was removed as the timing is now set. No need to keep it installed unless or, until another significant mod is in place.

Such as water/methanol injection.

Given that the AEM F/IC can run two completely different maps sets, a fellow could use the "B" map set for the water/methanol injection. That way, if the reservoir goes dry, the timing could be dialed back immediately so as to not risk detonation.

Detonation, we have not gotten into timing requirements yet, so I will kick that off.

The "rule of thumb" say to retard the timing 1 degree per pound of boost. This is a good, safe, starting point but the actual timing map will need to be tuned for the fuel used as well as all of the rest of the parameters that get in the way.

Cam Timing and Altitude being, IMO, the two heavies here.

Water/Methanol Injection Theory of Operation article:
http://www.importtuner.com/tech/impp_1101_water_methanol_injection/viewall.html

For those that like Wikipedia, they have a repetitively good article. Commercial sources for the kits are nearly everywhere. Prices range.

Feel Free To Ignore:
"Rule of Thumb" From The Phrase Finder:

Meaning:
A means of estimation made according to a rough and ready practical rule, not based on science or exact measurement.

Origin:
The 'rule of thumb' has been said to derive from the belief that English law allowed a man to beat his wife with a stick so long as it is was no thicker than his thumb. In 1782, Judge Sir Francis Buller is reported as having made this legal ruling and in the following year James Gillray published a satirical cartoon attacking Buller and caricaturing him as 'Judge Thumb'. The cartoon shows a man beating a fleeing woman and Buller carrying two bundles of sticks. The caption reads "thumbsticks - for family correction: warranted lawful!"

It seems that Buller was hard done by. He was notoriously harsh in his punishments and had a reputation for arrogance, but there's no evidence that he ever made the ruling that he is infamous for. Edward Foss, in his authoritative work The Judges of England, 1870, wrote that, despite a searching investigation, "no substantial evidence has been found that he ever expressed so ungallant an opinion".

It's certainly the case that, although British common law once held that it was legal for a man to chastise his wife in moderation (whatever that meant), the 'rule of thumb' has never been the law in England.

Even if people mistakenly supposed the law to exist, there's no reason to believe that anyone ever called it the 'rule of thumb'. Despite the phrase being in common use since the 17th century and appearing many thousands of times in print, there are no printed records that associate it with domestic violence until the 1970s, when the notion was castigated by feminists. The responses that circulated then, which assumed the wife-beating law to be true, may have been influenced by Gillray's cartoon or were possibly a reaction to The Rolling Stones' song 'Under My Thumb', which was recorded in 1966.

The phrase itself has been in circulation since the 1600s. In 1692, it appeared in print in Sir William Hope's training manual for aspiring swordsmen, The Compleat Fencing-master:

"What he doth, he doth by rule of Thumb, and not by Art."

The origin of the phrase remains unknown. It is likely that it refers to one of the numerous ways that thumbs have been used to estimate things - judging the alignment or distance of an object by holding the thumb in one's eye-line, the temperature of brews of beer, measurement of an inch from the joint to the nail to the tip, or across the thumb, etc. The phrase joins the whole nine yards as one that probably derives from some form of measurement but which is unlikely ever to be definitively pinned down. The Germans have a similar phrase to indicate a rough approximation - 'pi mal daumen' which translates as 'pi [3.14…] times thumb'.

The earliest such 'measurement' use that I can find referred to in print is in a journal of amusing tales with the comprehensive title of Witt's Recreations - Augmented with Ingenious Conceites for the Wittie and Merrie Medicines for the Melancholic. It was published in 1640 and contains this rhyme:

If Hercules tall stature might be guess'd
But by his thumb, the index of the rest,
In due proportion, the best rule that I
Would chuse, to measure Venus beauty by,
Should be her leg and foot:

The 'rule of leg' never caught on.

Pretty Useless, eh?
 
Given that the AEM F/IC can run two completely different maps sets, a fellow could use the "B" map set for the water/methanol injection. That way, if the reservoir goes dry, the timing could be dialed back immediately so as to not risk detonation.
That is the intention on my build. Have a fail save map that dials timing back and/or adds fuel. I never really had a use for the washer reservoir low indicator.. I will now though.
 
I like it. Intend to add a reservoir for the wipers then, eh?

I would be interested in the system you are are going to use. I am assuming a single injector installation?

Examples:
http://www.snowperformance.net/jeep-gasoline-all-models

http://www.coolingmist.com/

http://www.aemelectronics.com/water-methanol-injection-kits-23/water-methanol-systems-for-gasoline-engines-51/

http://www.summitracing.com/search/part-type/water-injection-systems?PageSize=100

It appears that Snow and AEM have the majority of the market with Nitrous Express and Painless bringing up the rear.

It also looks like most use a one gallon tank and cost vary all over the map... How about a cool $1,000 for a kit?

Shorter, sorted, list from Summit:
http://www.summitracing.com/search/part-type/water-injection-systems/brand/snow-performance/boost-pressure-reference-switch-included/yes/universal/yes/fuel-type/gasoline/fuel-delivery/fuel-injection?PageSize=100

I have looked at systems that have you install additional injector bungs as they port time the injection.

Very Spendy indeed...
 
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