Sales@Tick

iTrader: (3)

Yes sir I am. That cam is ok, but I like a lot more split than that on a positive displacement blower and for a LS7.
Yep, blue00ZZleeper hit it on the head. The total duration of the intake lobe and the installed centerline determine the dynamic compression ratio when it comes to cam timing. Quench also plays a part in the actual dynamic compression ratio which is how far the piston is in the hole or out of it combined with the head gasket thickness.

Bob@BruteSpeed

iTrader: (16)

I agree, an the F-1A fits in place of a D-1SC much easier than going with a larger blower such as an F-1C on up. Bob

N2OBaby

From what I've seen in GMHTP the F-1A is nothing to sneeze at.

If I were running High Boost lets assume 17-26 lbs wouldn't a 8.7:1 be better than a 10.2:1 as far as static CR(assuming a 60/40 mix of pump E-85 & E99)???

Sales@Tick

iTrader: (3)

Nope!

Again it's all in quench(head gasket and how far the piston is in the hole) and dynamic compression.

If you wanted to run 17-26lbs on corn I'd shoot for a dynamic of 8.0:1-8.2:1.

Blown06

iTrader: (32)

...and whats your theory regarding deck height? in the hole, zero, out of the hole?

Sales@Tick

iTrader: (3)

On boosted applications and heavy nitrous(350-400+) I'd like to see it in the hole to increase quench and squish. Basically by doing this you're slowing down the flame front and flame speed and giving yourself a wider tuning window allowing you some room for error. If you have a tight quench on a boosted motor or nitrous, the flame front and flame speed will be so fast and burn so quickly that it will be harder to get the correct amount of timing in the motor and it will become very picky and sensitive to timing changes, weather changes, boost changes and fueling.

N/A motors benefit from tighter quench because they aren't using an accelerant to speed up the combustion process like nitrous and/or aren't cramming massive amounts of air creating a lot more cylinder pressure and flame front speed than a N/A motor ever could. With tighter quench a N/A motor becomes more efficient and won't need quite as much timing to make the same peak power as it did with less quench distance.

helga203

There's a lot good advice on here but the bottom line is your going to have to have all your ducks lined up perfectly to active your Hp goals if you go with a smaller blower like the f1-a,d etc... Once you start getting up to the f-1c,r, f-1x or the f-2 there is forgiveness in your set up if you don't get your compression, cam heads or whatever down perfect. After reading this thread it's starting to get complicated. I have the f-2 now and love it i should of done that from the beginning. Now i don't have to push every once out of my blower to scare me when i punch it.

N2OBaby

If I were thinking of an AES/ERL 410 I'd look into using an F-1X or F-2 or F-2R for 1000+RWHP.

Sales@Tick

iTrader: (3)

You say it's complicated, I say it's the correct way to spec a build.

These are all the little details that people skip or leave out and then wonder why someone else's exact same combination makes more power than theirs does.

N2OBaby

The devil is in the details for shure.

Blown06

iTrader: (32)

You may call me crazy, but my engine builder was telling me that having the piston out of the hole a little (his words were "piston top in the gasket") helps with sealing these 4-bolt motors. You ever see any of that?

May not be ideal from a tuning (timing) aspect, but from a durability aspect helping to not push water. Provided it's in the hands of a capable tuner.

N2OBaby

Is it possible to buy a supercharger biggier than needed then pulley it down to provide the boost wanted?

For example a D-1SC or F-1A would easily help a 390 LQ9 reach 752-820 FWHP but a Cog Belt(Aka. Race Drive) F-2 should be good for 800-1100RWHP, with the right pulleys could this F-2 do the same?

Bob@BruteSpeed

iTrader: (16)

An F-1A can easily get you 900+ rwhp with the combination, but yes, you can do that with an F-2. Keep in mind the larger blowers use up more power to turn them. You will get to a point where a smaller blower can make more power than an F-2 at the same boost level. The new F-1X would be a great blower to use where you're anticipating building a six bolt block/head combo to where you can use the blower to it's potential. Bob

chuntington101

Hi Martin, I was always lead to believe that the flame front on a boosted application is slower than a NA setup due to the denser fuel air mix taking longer to burn. Also peak cylinder presure will be lower but for much longer. Is this not the case?...

Also what are the impacts of a lower TDC piston hight and fuel air mixture? Again I hear that a tighter setup give more even fuel air mix and thus a better dept. resistance. Is this wrong on ls engines?

chuntington101

Bob, Do procharger provide maps fit their superchargers? It would be interesting to see at what airflow / boost levels each SC excels! From the sounds of it alot of people are running a (slightly) smaller blower than what is ideal?...

N2OBaby

The F-1A is more capable than I was giving it credit for.

Sales@Tick

iTrader: (3)

Never heard of that.
Well part of this is correct. A richer fuel mixture will have a slower flame front, and it seems a lot of people on this site run their motors too rich(at least IMO). This will cause a lower speed flame front yes. I always found best mph and response with AFR in between 11.8-12.2 while running the timing lower than most do(again on this site) on my PT76 equipped LS1 and it had 10.33:1 SCR and 8.18:1 DCR.

It seems some have been led to believe that if the engine knocks you just need to richen the mixture and that more fuel cools the combustion when in reality all you're doing is lowering the flame front speed and lowering the pressure wave that occurs during combustion. They think this is "proper" when they could of leaned it out some more and retarded the timing and possibly made more power, but too many factors come into play to theorize that case to be made.

Again your second statement is partially correct. Tighter quench(squish) effectively takes the fuel and air mixture and squishes it from the outside edges of the piston/chamber faster into the spark plug pocket making more turbulence which helps mix the F/A mixture more effectively which makes the burn more efficient. This requires less cylinder timing to create peak power and light off that mixture. In reality if you just tightened quench and left ignition timing alone where it was with a looser quench it would detonate more.

The reason it "lowers" the chance at detonation is it evenly mixes and better mixes the F/A charge. When you do this there is less of a chance of there being left over fuel in the combustion chamber/cylinder that the heat from the spent combustion can re-ignite causing detonation(separate pressure wave than the main pressure wave generated by main combustion).

All of this is great don't get me wrong quench is there for a reason, but in a power adder application you already have higher cylinder pressure than N/A, you have accelerants speeding up the flame front, and in general a more violent environment for F/A mixture to combust. In this type of environment you don't need something that is super speeding up the flame front even more or causing an even faster burn because you're already doing that with the power adder. Tight quench versus loose quench is easily explained by this analogy. Take a coffee can with fuel in it and pour it slowly on a camp fire...it will flame up at a slower speed than if you took that coffee can with fuel in it and throw it like a baseball at the fire. Throwing it will make the resulting flame much more violent, much higher and burn much faster. This is the difference between loose quench and tight quench.

All that being said with nitrous/boost, since it is already speeding up the flame front, higher cylinder pressure due to higher compression etc. you want to try and control the flame front speed as much as possible with factors you as the user have control over such as timing, fuel mixture and the amount of nitrous or boost put through the motor. When you have a set mechanical factor such as tight quench to deal with that is already speeding up the flame front by itself and that you can't change without actually tearing the motor apart and fixing, you lose that control over the combustion event and makes it that much harder to control and be predictable.

I hope this helps anyone that has wondered about this and helps to open some eyes.

Again there are two thoughts of engine building when it comes to power adders. Build the most powerful N/A engine(high compression, tight quench) you can then toss a power adder on it and hope to be able to control the faster burn rate that will coincide with those factors. Or you can build it a little on the safer side, little looser quench(some of the quench numbers I have heard on extremely high boost and nitrous applications will blow your mind, I'm talking .125+) with a wider tuning window and spray a little more nitrous or add a little more boost to it.

In a jet restricted class or a compressor limited class you can't do this so the train of thought is build the most powerful N/A motor you can.

Ok enough for now, lesson for the day is over.

chuntington101

Thanks for the info Martin! Think i understand most of it. Have you ever exsperimented with chemical injection (water) to redcue the flame front speeds? I hear the WRC rally guys do this and it lets them run about 45psi intake manifold preusres on 12:1 + compresion ratio engines with peak power below 5200rpm! They run a torque per ltr ratio that is rediculus and all this on pump fuel! they are intake restircted (35mm restrictor i think) on a 2.0ltr engine.

Chris.

Sales@Tick

iTrader: (3)

I have used water/methanol injection on my turbo car, and found that if I injected it too soon that the flame front didn't have enough speed in it at that point to where I basically put it out almost entirely and got a really bad bog which then fouled my plugs and O2 sensors immediately.

I've heard of using water injection to basically have a controlled "bog" we will call it although the car doesn't bog it just slows the flame front down as you mentioned and brought up along with raising cylinder pressure from the water turning to steam and expanding in the cylinder.

Those rally cars look like a lot of fun!

It seems like the way people are making a lot of power in today's heads up racing classes with good control over the tune-up are running higher than normal compression numbers, reduced quench and a lot of boost or nitrous with the best fuel they can. At least in the non jet restricted/compressor heads up classes they are.