Turbo manifold

[ifoundastick]

One question that ponders in my mind about this whole setup is your still going to have to deal with a carburetor. I mean yeah your going to have a alot of horsepower but if your going to be really wheeling that beast aren't you going to have to deal with the carb flooding and the troubles that comes with carburated engine?

 

[MogifiedXJ]

One question that ponders in my mind about this whole setup is your still going to have to deal with a carburetor. I mean yeah your going to have a alot of horsepower but if your going to be really wheeling that beast aren't you going to have to deal with the carb flooding and the troubles that comes with carburated engine?

From what I gather it's going to be a "street" jeep.

http://www.naxja.org/forum/showthread.php?t=90989

 

[zthang43]

He may be referring to "effective compression" - which is a function of boost. I don't recall how it works (and I don't have the book handy at the moment, or I'd explain it,) but it is a real phenomenon.

However, the "basic" or "geometric" CR of the engine does not change, unless you change something within the acting cylinder (head dish dims, piston dish/dome, bore size, stroke.)

Effective compression ratio, however, is a function of several other things. For instance, you can build an engine combo with a "basic" or "geometric" CR of 9.0:1, but that can be changed (always to soemthing lower than 9.0:1) by changing camshafts, for instance. The key there is the timing of the "Intake Valve Closing" event. I believe I cover this in my book - but I'll add it as an update if I haven't (gotta finish the Tech Archive updates first...)

5-90

I think you are talking about Volumetric Efficiency, which is a known and accepted term in the automotive industry. The idea of "Effective compression", while I understand what you mean, is a bit skewed and misleading. 13.8:1 "effective compression" under 6psi boost does not behave the same as a real 13.8:1 compression ratio. That high compression ratio would destroy most engines very quickly running on pump gas, but the same "effective compression ratio" achieved by running 6psi boost should be perfectly safe in a properly built engine running on cheap pump gas.

The difference is that the forced induction motor is forcing a larger volume of the air/fuel mixture in the cylinder, as opposed to a NA motor squeezing a smaller volume to get a high compression ratio. Theoretical maximum Volumetric Efficiency for any NA motor is 1 (although with proper tuning of the intake pulses a slightly higher VE can be achieved); but a forced induction motor can have a VE greater than 1 (or 100%, .9 would be 90%). This is still related not only to boost but to cam profiles, head geometry, valve sizes, intake configuration, etc, etc, so even a boosted motor that is poorly designed can have a VE less than 1.

Hopefully this explains why the concept of "effective compression" is flawed; sure, it's an easy calculation that sounds good, but it doesn't actually make sense unless you account for the Volumetric Efficiency of the engine without boost.

Sorry, I didn't mean to sidetrack this thread; it just bugs me when people throw around artificial compression ratios that are completely bogus, just because they think it sounds cool, like "yeah, i'm running 15psi boost so i've got 18:1 compression ratio". A motor with that kind of compression ratio could run on diesel fuel, not gasoline.

 

[5-90]

I think you are talking about Volumetric Efficiency, which is a known and accepted term in the automotive industry. The idea of "Effective compression", while I understand what you mean, is a bit skewed and misleading. 13.8:1 "effective compression" under 6psi boost does not behave the same as a real 13.8:1 compression ratio. That high compression ratio would destroy most engines very quickly running on pump gas, but the same "effective compression ratio" achieved by running 6psi boost should be perfectly safe in a properly built engine running on cheap pump gas.

The difference is that the forced induction motor is forcing a larger volume of the air/fuel mixture in the cylinder, as opposed to a NA motor squeezing a smaller volume to get a high compression ratio. Theoretical maximum Volumetric Efficiency for any NA motor is 1 (although with proper tuning of the intake pulses a slightly higher VE can be achieved); but a forced induction motor can have a VE greater than 1 (or 100%, .9 would be 90%). This is still related not only to boost but to cam profiles, head geometry, valve sizes, intake configuration, etc, etc, so even a boosted motor that is poorly designed can have a VE less than 1.

Hopefully this explains why the concept of "effective compression" is flawed; sure, it's an easy calculation that sounds good, but it doesn't actually make sense unless you account for the Volumetric Efficiency of the engine without boost.

Sorry, I didn't mean to sidetrack this thread; it just bugs me when people throw around artificial compression ratios that are completely bogus, just because they think it sounds cool, like "yeah, i'm running 15psi boost so i've got 18:1 compression ratio". A motor with that kind of compression ratio could run on diesel fuel, not gasoline.

"Effective CR" is more applicable to cam changes than boost levels, but it's not the same thing as VE.

"Volumetric Efficiency" is the percentage of theoretical air moved per revolution versus air actually moved. Assuming your engine is supposed to move 400CFM, having 80% VE at one point means that your engine will move 320CFM.

"Effective Compression Ratio," as it is commonly used, is the ratio between the space left at TDC versus the space left in the cylinder at the time the intake valve closes. Closing the valve earlier (closer to BDC) will increase the ECR, and closing it later (farther from BDC) will decrease it. However, ECR, in this case, will NOT be higher than the theoretical CR. "Effective" compression ratio is more like "actual" compression ratio, in this case.

"Effective" compression, in the case of boost, relates to the pressure of the compressed gas mix at TDC versus atmospheric pressure, which is why ECR for boosted engines damn sure CAN be higher than the theoretical CR. However, I'm still explaining this rather poorly, but I haven't gone through my notes. I probably did a better job in my book, but I didn't write that off the top of my head...

5-90

 

[zthang43]

"Effective CR" is more applicable to cam changes than boost levels, but it's not the same thing as VE.

"Volumetric Efficiency" is the percentage of theoretical air moved per revolution versus air actually moved. Assuming your engine is supposed to move 400CFM, having 80% VE at one point means that your engine will move 320CFM.

"Effective Compression Ratio," as it is commonly used, is the ratio between the space left at TDC versus the space left in the cylinder at the time the intake valve closes. Closing the valve earlier (closer to BDC) will increase the ECR, and closing it later (farther from BDC) will decrease it. However, ECR, in this case, will NOT be higher than the theoretical CR. "Effective" compression ratio is more like "actual" compression ratio, in this case.

"Effective" compression, in the case of boost, relates to the pressure of the compressed gas mix at TDC versus atmospheric pressure, which is why ECR for boosted engines damn sure CAN be higher than the theoretical CR. However, I'm still explaining this rather poorly, but I haven't gone through my notes. I probably did a better job in my book, but I didn't write that off the top of my head...

5-90

I hear ya, but Effective compression ratio in the case of boost is still a misleading and completely useless calculation that I hear used by people who think it sounds cool and don't understand what they are talking about.

You can't equate 13.8:1 "effective compression ratio" under boost to 13.8:1 actual compression ratio in a NA motor. The combustion process would be much faster, and peak at much higher pressure (with detonation a likely result), than the boosted motor, which will have a combustion process that lasts longer with lower pressure and produces more power.

 

[tealcherokee]

Holy crap my thread took off.

for the 5.1 im going to be running hescos alum block if it ever comes out

as far as the evvective compression, you guys got it covered

 

[5-90]

I hear ya, but Effective compression ratio in the case of boost is still a misleading and completely useless calculation that I hear used by people who think it sounds cool and don't understand what they are talking about.

You can't equate 13.8:1 "effective compression ratio" under boost to 13.8:1 actual compression ratio in a NA motor. The combustion process would be much faster, and peak at much higher pressure (with detonation a likely result), than the boosted motor, which will have a combustion process that lasts longer with lower pressure and produces more power.

True, very true. "Effective compression" due to cam changes is a little more realistic - there are too many variables (most notably altitude and ambient temperature) to go into calculating "effective compression" due to boost.

5-90

 

[DirtyMJ]

Teal, gotta ask about your intended ignition system with a carb...


What exactly are you doing? How will you set your timing? (Don't need numbers, I need process) Or are you going to use some fancy computer controlled setup which allows you to do that in real time and blah blah blah...?


I have a similar project, which is nothing alike other than it involves ditching the Renix FI. The only hitch I have right now is that there's no timing marks on my harmonic balancer, and I'm having no luck finding an ideal solution...

 

[MogifiedXJ]

You might want to consider adapting something like an old hilborn mechanical fuel injection to your turbo setup instead of a carb. It's about the simpliest injection I can think of. Everythings mechanical even the fuel pump which is belt driven of the engine.

 

[DirtyMJ]

How about we convince teal to run propane? 107 octane, very clean fuel, and making a draw through setup is VERY easy. Having the mixer after the turbo gets tricky though, but I know there is a system out there for it.



Other than propane isn't big south of the border.

 

[tealcherokee]

theres 2 ways to go carbed. 1, msd set up. 2, stock 258 distributor

so the cheap way, is the 258 distributor

 

[DirtyMJ]

theres 2 ways to go carbed. 1, msd set up. 2, stock 258 distributor

so the cheap way, is the 258 distributor

Well, I've got a GM HEI dist/etc from a 250 I6. Basically bolts in. However, I'm a little bit weirded out as the harmonic balancer has no timing marks, and I'm not even sure I can put timing tape on it.


I'm looking into it.

 

[tealcherokee]

Well, I've got a GM HEI dist/etc from a 250 I6. Basically bolts in. However, I'm a little bit weirded out as the harmonic balancer has no timing marks, and I'm not even sure I can put timing tape on it.


I'm looking into it.

it does have a mark, its just hard to see

 

[tealcherokee]

heres a little taste of what im working on

 

[Michaelarchangelo]

Where are you going to mount the turbo in that setup? Will It clear the intake? I like the look of this one better, but you are going to need to collect the gases together before you reach the turbp.

 

[tealcherokee]

Where are you going to mount the turbo in that setup? Will It clear the intake? I like the look of this one better, but you are going to need to collect the gases together before you reach the turbp.

as i said, its just the start.

there will be a collector of some sort on the end

 

[MogifiedXJ]

What software are you using to design this on? I've got some copies of pro-e if you don't already have it.

 

[tealcherokee]

What software are you using to design this on? I've got some copies of pro-e if you don't already have it.

i use auto cad, ive been using it since i was about 13 lol, ive never heard of pro-e, i dont even look at anything else im so fimiliar w/ cad

 

[MogifiedXJ]

i use auto cad, ive been using it since i was about 13 lol, ive never heard of pro-e, i dont even look at anything else im so fimiliar w/ cad

I used to use autocrash too before I learned Pro-E. It's a world of difference...It takes a little while to get the basics down but its truly an amazing software. Are use using autocad inventor or just autocad to do your drawings?

 

[tealcherokee]

just autocad, good old autocad, version 2007, but on the old style setting