CAI vs Short Ram (a little long)

[bullettdsm]

Ok, let me jump into the CAI vs Shortie (it's not REALLY ram air ) a little bit. For those of you who say E-bay pipes are fine; a pipe is a pipe. That may be true BUT I've run into a bit of a dilemma with my two intakes. With my set-up, I have been running the ram air up to 8,000 on an worn engine with 133k on it. I read about the arguments for the CAI and I understand the thought process of cooler air being better, so I went out and bought and installed an E-Bay CAI. Well, there went my 8200 redline. Now I could only reach 7,000 and then it would start popping (I thought I finally made them valves start floating ). Ran about 600 miles no change. Just put the ram back on and lo and behold smooth up 8K again. No popping. Same filter just different piping.

A couple points of interest (and maybe dr1665 already knows this?)The CAI has an extrabend in it in comparison to the ram. Thus giving you one more conflict for airflow. Also (and I think this is more likely the problem), The CAI inner diameter is 2 1/2 inches. Whereas the Ram id is 2 3/4 inches. Both dimensions bigger that my TB port but it seems that the ram air hook-up to the TB actually constitutes (what we used to call on carbs) a velocity stack (kind of like the "hump" that we generally port out when making a TB bigger). This change in diameter speeds the air along, while not changing the pressure, it changes the velocity. Though usually this is talked about when looking at low RPM response, it can also be associated with top end.

My point of all this bullcrap? Yes a pipe is just a pipe but size matters (leave the joke alone too easy). If I was deciding on a CAI I would take into consideration the size and the amount of bends. If I was to put a CAI on again I would be sure that the piping was bigger. It is hard to find that out on E-Bay.

I would also be curious to hear from others (like Brian because I see that you are also running the E-Bay short Ram still) who have done both.
MB

Oh yeah, I apologize if I put this in the wrong forum. I am still working out the different forums. But I think this info would be of interest to newbies on up.

 

[esi-slowboy]

A bigger diameter tube allows more air to go in but at a slower speed (more area). The air flow speed needed to make peak volumetric efficiency occurs at a higher rpm compared to a smaller diameter tube.Thats why your 2.5 in. CAI ran out of steam not enough capacity.Since you have an 8k redline(yeow)2.75short ram worked out, more flow volume by increased diameter and shorter tube

A longer tube creates faster air flow compared to a short tube (i.e. more pressure differential from the opening to the TB end) and peak volumetric efficiency will occur at an earlier (i.e. lower) rpm. This is why a longer CAI has an advantage in the midrange over a short ram.
Theres alot more to this topic plenty of variables

 

[Redmachine]

Just a word of wisdom. Yes our cars technically redline at 7200 rpm, but the majority of our power lies in the 6500 rpm range, why take it above that? Plus a unmodified engine, might not be able to handle all of those extra revs..... were not hondas

 

[bullettdsm]

Just a word of wisdom. Yes our cars technically redline at 7200 rpm, but the majority of our power lies in the 6500 rpm range, why take it above that? Plus a unmodified engine, might not be able to handle all of those extra revs..... were not hondas

Cause I like to blow stuff up!!!
MB

 

[Venum]

Just a word of wisdom. Yes our cars technically redline at 7200 rpm, but the majority of our power lies in the 6500 rpm range, why take it above that? Plus a unmodified engine, might not be able to handle all of those extra revs..... were not hondas

I'm with him, I have never put my car over 7200 and, actually, I have only redlined once just to say I did it.

A CAI gives you more hp in the midrange like the other two said which is why it's more beneficial for our cars because we're not made to be revved up to 8k rpm every shift.

 

[xXeclipstasyXx]

I'm with him, I have never put my car over 7200 and, actually, I have only redlined once just to say I did it.

A CAI gives you more hp in the midrange like the other two said which is why it's more beneficial for our cars because we're not made to be revved up to 8k rpm every shift.

ive never even tried getting my motor above 7200, redline is there for a reason, not becasue the engine cant go higher b/c it can, but b/c it is not producing effiecient power... dsm's are torquey motors, theyre not hondas you dont need to rev the crap out of them to get the best power

 

[GSGoinFast]

I'm with him, I have never put my car over 7200 and, actually, I have only redlined once just to say I did it.

A CAI gives you more hp in the midrange like the other two said which is why it's more beneficial for our cars because we're not made to be revved up to 8k rpm every shift.

I've redlined mine a few times, although most were just watching how high i could get it to rev on teh S-AFC... said i got 7424 rpms... so much for the 7200 redline

 

[Venum]

I've redlined mine a few times, although most were just watching how high i could get it to rev on teh S-AFC... said i got 7424 rpms... so much for the 7200 redline

Yikes that's high! Were you in neutral when you did it? And after that it cut you off, right?

 

[GSGoinFast]

Yikes that's high! Were you in neutral when you did it? And after that it cut you off, right?

actually i was in first but i only did it twice to see how high it would go. after that it cuts off and the car feels like it hit a wall.

 

[bullettdsm]

Just for understanding purposes, I run the AF/X ECU and I do have a 97. So my actual rpm range should be up around 8200. Do I still have power past 7K? Well, yes I do still pull. With my 60mm and the port and polish I put into the intake and exhaust (along with other breather items) I can pull up to 8k in 1st (now, not full pull power but it does allow me to maintain my power range on a speed shift to 2nd). In 2nd gear I can make her go to 8k but she starts to poop out around 7. Never tried 3rd.

I guess I may be a bit of a looney but I get kind of curious about what a stock engine can put up with. I see people on these forums claiming that you must have the super heavy duty hercules valve springs (maybe even duelies) to go 8k. I dunno, I look at the design and the spring tension that is made for 7k and I say I'll bet these could take ya up to 8.5 to 9k. And the valves, what can they put up with? The design of the stock crank? Hey you guys want to see crankwalk, check out a vw dub bug that does 7k and up. HaHaHaHa! I'll tell you what, this stocker crank can take you places (watch me get flamed by all the crankwalkers out there ).

Yeah, I hear ya now; longevity, how long is it going to last? Yep, good question, I guess I'll find out.

I got other ideas about a lot of the nece$$ity for some of these hi-performance parts (unless your intent is to run the strip. Then it's a whole new ballgame) but I don't want to piss anybody off. And really no disrespect intended to anyone out there, I just enjoy playing.
MB

 

[dr1665]

I think people have pretty much got your problem figured out. By using different pipe diameters, you're modifying the velocities of the intake charge. Combined with your overkill TB (more than 57mm on ANY all motor car is ridiculous, imo), you have radically changed the way that the engine gets its air supply. You should know that a "bigger is better" philosophy with this sort of thing is a bad idea.

Also, I'm pretty sure that velocity stacks are engineered to accelerate the air charge through the use of a nice, rounded lip at the opening which then tapers down to a reduced diameter. I wouldn't say you have a velocity stack going on, more like a hodge-podge intake set up. You are accelerating and decelerating the air back and forth before it gets to the intake runners. Not good. Not that it's really hurting anything (aside from when you get all kamikaze on your stock internals), just seems a bit crude.

You will make more power by replacing that stupid TB with a properly sized unit and the short ram, imo. If you want to get all custom and do some experimenting with things, do some research on "Hemholz Resonators." Not sure if I spelled that right, but you might do some math and pick up a couple properly sized mandrel bends. Build your own intake and see what happens. If your poor stock internals hold up. Despite being able to wrap it out to 8200 (sure you're not hitting ignition cut?), you're really not making much more power at those speeds than you are at 7500 (where I wind mine out to until the MS 9000 comes on board).

You are SO begging to drop a valve and munch the shit out of that poor 420a.

 

[bullettdsm]

I think people have pretty much got your problem figured out. By using different pipe diameters, you're modifying the velocities of the intake charge. Combined with your overkill TB (more than 57mm on ANY all motor car is ridiculous, imo), you have radically changed the way that the engine gets its air supply. You should know that a "bigger is better" philosophy with this sort of thing is a bad idea.

Also, I'm pretty sure that velocity stacks are engineered to accelerate the air charge through the use of a nice, rounded lip at the opening which then tapers down to a reduced diameter. I wouldn't say you have a velocity stack going on, more like a hodge-podge intake set up. You are accelerating and decelerating the air back and forth before it gets to the intake runners. Not good. Not that it's really hurting anything (aside from when you get all kamikaze on your stock internals), just seems a bit crude.

You will make more power by replacing that stupid TB with a properly sized unit and the short ram, imo. If you want to get all custom and do some experimenting with things, do some research on "Hemholz Resonators." Not sure if I spelled that right, but you might do some math and pick up a couple properly sized mandrel bends. Build your own intake and see what happens. If your poor stock internals hold up. Despite being able to wrap it out to 8200 (sure you're not hitting ignition cut?), you're really not making much more power at those speeds than you are at 7500 (where I wind mine out to until the MS 9000 comes on board).

You are SO begging to drop a valve and munch the shit out of that poor 420a.

I thought esi-slowboy explained the concept rather well. I was just wondering if someone had some input on the length and bends. The one thing I learned over the years is try to make it short and straight. The most efficient use of air to get the most air through as possible. I see people talking on here about the benefits of the CAI but I do not see any discussions on the length and the width (kind of the point of my convoluted post). As for the "bigger is better philosophy"; you should know by now that I don't subscribe to that theory. BUT I do like to find out how big is too big. That limit I have not seen on any dyno results (other than butt dyno and theory based arguments).

As for the velocity stacks concept, I should have really said LIKE a velocity stack just to try to explain the concept. I did not mean to say that I made a velocity stack. What mitzu themselves do with the stock TB is put that "shoulder" in their TBs to speed up the air to enter the chamber of the intake. Now what is happening with TB/short ram set-up that I have, is the shoulder is located a little further away from the butterfly than stock (that shoulder being a smooth transition via the coupler from the ram 2 3/4 to the TB). You may consider that hodge podge but it seems to be the design that mitzu has only with bigger diameter intake and I moved the shoulder out a little (and again with other breathing additions - port match etc.).

I apprecate the input on experimenting on diffent intakes ( I haven't searched yet but is it Hemholtz? I'm not sure). But what I really want to do is get to the god damn dyno and test the 60mm and the 57mm and the 55mm that I made. I also want to test the ram vs the CAI. I will be testing on my old engine but that will have to act as the constant. The only problem with this is I need to get my wife's AWD on the road. Gotta get this tuning down . (just evo 16g with appropriate ad-ons but can't seem to lean it out to my liking yet). Then she can stop using my car and I can take it.

As for the 8200 redline. I haven't gone to it. That is what I understand the limit to be until fuel cut. But I do go to 8k and like I said before though the power may not be moving up, it allows me to speed shift right into my power range for second (in honesty, the shift point seems a little better at 7800, I'm kind of playing around with that.

And yep, I suspect that the first thing to go will be a valve. But that just goes to show you how well designed these engines are. These rods and cranks seem to be able to take some abuse. It is a really fine design and when this one goes, that is what the OTHER engine is for. Though I am honestly not working on that engine yet. I do want to see how well your's does and powell's does before I decide what route I want to take.

In the mean time, I'll just wee-wee along .
MB