Flow and superchargers...

[Husky]

I learned when I first asked about superchargers that an M62 will be out-flowed by the LQ1. Will and M90 Gen3 as well? Gen5? Is the M112 the only way to go, or could I use an M90?

[Fierobsessed]

An M90 would do ok though.

[Fierobsessed]

My manifold design (autocad)

http://members.aol.com/nstarfiero/manifold.dwg

[Husky]

Hmm... What keeps it from sittign lower? Is it too wide? Is it possible to remove enough from the side of the charger case and from the sides of the cam carriers to get an M90 sitting down in there? I'm gonnna start test fitting stuff soon...

[Fierobsessed]

As its shown sitting, the manifold is my origional (non drafted) design. The autocad file, if you can read it is the re-design. it allows the blower to be mounted significantally lower. I expect to have to mount the blower at the lowest posible position, witch will be where the bottom of the blower will still be just about even with the top of the cam covers. All the different pieces of metal that will make up the finished lower manifold will be welded in place, the only pieces that will be removable is the fuel rail (blocks?), and the injectors. The whole unit will become the lower intake. The fuel rail will be inside the manifold, and when it is removed, will leave 1.3" holes that you can pull the injectors out through. It's a pretty ingenius layout if I must say so myself. The bolts to remove the lower intake will reside both inside the manifold and outside it as well. My goal was to maximize flow, intake volume, simplicity, and minimize sealing surfaces, origionally I wanted to make the manifold two bolt togather pieces. I decided against that just because the huge likliness of leakage, and it still had to be strong enough to hold the blower up while the belt is tugging on it with some impressive force.

Fact is, you cannot mount the blower between the cam towers, its just too wide at the flange, and the lowest you can mount it, the injectors will be in the way. So if you find another place to put the injectors, great. If you want to mount the blower charge side up,like the ford's 3.8, you can do that too, but then things get more complex.

Draw your measurements from this pic

[prodigy_16]

damn you are on top of it! that should cure the dohc engine of its lack of low end torque. Its nice to see other people think like me (or vice versa )

[Husky]

With some creative work with a dremel, a lot of cutoff wheels, and a spare set of cam carriers, I've got it sitting about two inches lower than what it looks like you've got there, but I don't know about the feasibility of this setup. Either way, it looks like it's time to start looking for a cowl induction hood. I'll post pics as soon as I have something to show for my work.

[Mach10]

It's not that the LQ1 lacks torque...

It's that the W-bodys that it comes in are FAR too heavy.

Hence the Fiero

[Husky]

Well, it doesn't lack torque at all, but it lacks the FEEL of torque, probably somethign to do with the fact that torque doesn't peek until 4000 RPM, compared to, say, the L67 which peeks as low as 3200 RPM. And the 3100 in my friend's car FEELS torquier than my LQ1, even though it developes less torque and it peeks at the same RPM. I Don't know...

[dohcfiend]

mach10 is pretty much on the money. and you are almost on the yourself husky.

the "feel" you are referring to is low rpm torque only way to really get that is in the cams, although a roots blower definately would help.....just a tad.

the final saying should be something like this. it's not that the lq1 lacks torque, it is just that it doesn't make it at low rpms.


don't want to discourage you or anything but if u want low rpm power, perhaps u might want to consider a different engine altogether as it is just not what the lq1 was designed for in any aspect. you could get a pushrod v6 to make low rpm power plus it would be lighter and cheaper. i mean, not alot of sense to have a dohc motor if the max power is coming in under 5k.

[Husky]

don't want to discourage you or anything but if u want low rpm power, perhaps u might want to consider a different engine altogether as it is just not what the lq1 was designed for in any aspect. you could get a pushrod v6 to make low rpm power plus it would be lighter and cheaper. i mean, not alot of sense to have a dohc motor if the max power is coming in under 5k.

You'd like to think I would ever own anything but an LQ1 again. I'm not all about torque, I have no problem with a higher powerband. I like it in fact, easier launches. I just REALLY want to see a blower sitting on the top of this motor.

[dohcfiend]

that would be phucking sweet. those deep breathing 4 valve heads would be belting out power with a s/c.

it would rape l67's and leave them bleeding,crying and naked on the beach at 2am.

[Husky]

And every time I did that, I'd smile.

[Fierobsessed]

I have my opinions on boosting the 3.4 DOHC. Figured I might share them:

The reason I chose to go with the modified Roots supercharger (Eaton M112) as opposed to a turbo... Considering how huge the ports are on a 3.4 DOHC it needs more air coming into the heads reguardless of RPM to become more volumetrically efficient. So boost is one good answer, or rev it to high heaven. To maximise streetability I definatly didn't want to go the N/A route since I would have to rev it quite high to make the real power, probably have to increase compression and find a solution to the lack of aftermarket cams problem. So boost seems to be the practical answer all around for the 3.4 DOHC. Also taking into consideration that the cams can be freely set, also plays towards performance for either N/A or Boost.

Why the Eaton M112? Took some time to make up my mind about this aspect.

Turbochargers generally speaking, have a progressive boost increase, constantly increasing there output DUE to there increasing output; exponentially till the waste gate opens. In my opinion, this works best with a motor that has great volumetric efficiency down low, but needs help at the higher RPM's. A turbo compliments that need, to put out a more linear power output.

A turbo on a DOHC engine isn't very complimentary, the volumetric efficiency of the motor down low is so-so at best. Putting a restriction on the exhaust isn't going to make this any better. It's not helping the turbo spool very well till the boost really starts to kick in, where the turbo will make the DOHC engine become Volumetrically efficient really quickly, then it's at full boost almost instantly. So the power starts off pretty weak, then comes on extreemly fast. It will make really big numbers, but they will be peaky as opposed to full ranged. Great for making good times at the track if you can keep it where it's making all that power. It's slightly lacking in responce time. That's why (and I am making a very braud statement about this) DOHC motors with turbos are very picky about turbo size, and streetability vs. track performance is a compromise. Either they spool quickly and run out of breath, or they spool late and make a whole lot of power. (Again, there is a point where the right turbo is, JUST RIGHT, so shh. if your a turbo guru. )

Then there are the superchargers, there are three practical types on the market today. your Roots (modified or standard) centrifugal, and your lysholm (whipple) superchargers. Each have there advantages that you must consider when choosing one, and there downfalls.

Centrifugal superchargers are a perfect cross between a turbo and a supercharger. They spool strictly based on RPM and have a progressive (non linear) output. In other words, if your engine puts holds back 10 PSI of boost, your flow will be a curve based on RPM. These superchargers are known for good Adiabatic Efficiency (in otherwords, they don't heat the air much past what the compression does). These are perfect for a pushrod motor, helping it make a fairly linear slope of torque. They work quite well on a DOHC engine, however the power curve will be a steep ramp as opposed to a good range on a DOHC motor. Simular to a turbo.

Lysholm superchargers (also known as Screw chargers or Whipple chargers) are very simular to a roots supercharger component wise, however the rotors are different, they actually produce boost internally reguardless of engine flow. it actually takes a volume of air and as it travels from the inlet of the SC to the outlet of the SC gets compressed a little, usually the ratio is about 1.35:1 or so. You will make 5.2 PSI of boost the instant the pedal is floored. The reason this is important is because it accomplishes 5.2 PSI of boost and cools it to an extent, from there it can build up inside the intake manifold to whatever boost level you actually desire, but some of the boost has been made in a more efficient fashion. The output is roughly a ratio of boost to flow times RPM. In other words, its output is almost linear. The downside, since there is always an internal compression, there is always a certain amount of power required to spin them, I have never seen this number documented, but it has to exist due to it's design. And often times, these superchargers can be cost prohibitive, since there are VERY FEW OEM applications for the Lysholm superchargers. Adiabatic Efficiency wise, they are somewhere between a Roots supercharger, and a Centrifugal.

Lastly there are the Roots superchargers. Fortunatly for us, there are MANY OEM applications for the Eaton (modified Roots) SC's. So they can be found pretty darn cheep. Roots superchargers are generally thaught of as being an oldschool form of boost, characteristically having very poor Adiabatic Efficiency around 50% and taking a lot of power to make reasonable boost. This is true. But, in this day and age, Eaton automotive has improved these oldschool boosters substantially. Today they have twisted helix rotors, they are epoxy coated, have an axial air inlet, and are totally self contained. This is important because it has improved there efficiency, practicality, cost, packaging and reliability to a point where they have become a hot item for OEM applications. The most important improvement for the Eaton SC is the bypass valve. When this opens, the drag created by the SC becomes minimal, costing about 1 MPG on the highway. The output is linear, just like the Lysholm but its Adiabatic Efficiency is not as good. Did I mension they are cheep?

So I felt that the 3.4 DOHC's power curve needed more low end grunt, and boost all throughout its range. I wanted the best streetability, (most torque range) best gas mileage on the open road and for a reasonable price. And then when it comes to appearance and sound, its hard to ignore the Eaton SC. Lysholm was way close in my considerations. Im trying to create a Modern Hotrod of sorts, and that requires a slightly old car, modern approaches and a blower sticking out the hood. (or sideways of of a Fiero's decklid)

As far as what I plan on doing to the engine, other then the blower I have lots of plans, few of witch I have actually started, so it's all up in the air till I can actually work on it. I plan on using a 3500 crank, modified for the 7X reluctor to fire a relativly normal DIS system. The rods will be aftermarket Eagle H beam rods for the 4.3L, modified to accept 3500 bearings, and fit to the crank. The pistons will be custom forged slugs, yet to be determined. Compression ratio probably between 8.7 and 9.0, still undecided. Mains and oil pan will be from a 3100, unless I decide to just girdle them internally, in witch case I will stick with the steel pan. Oil system will be relativly stock, as I don't see a need to modify it. But I plan on opening up the drainback passages to keep the oil in the pan where it belongs. I will make custom headers... but I don't know weather I will make them equal length or not, it depends on space in the engine compartment. I do not plan on making any changes to the heads whatsoever, (unless the oil drainback passages need cleanup) I am actually not planning on doing ANY top end work, with exception to the intake manifold, and the cam timing, and injectors. Managing this beast will be a 1227730 ECM, with a highly modified 89-90 TGP code. I plan on running 12-15 PSI and no more. I am expecting 350 at the wheels, 26 MPG or better, two 11 second runs and pass emmissions every year. I expect it to stay a daily driver. Thats asking a lot from any motor. I've seen L67's that come close to pulling this off. but with the 3.4 DOHC, I can see it happening. If all else fails, I still have my Quad 4 pace car, its a lot of fun to drive too.

Thats about all. sorry for going on and on about what I'm doing and why, but it's something I am passionate about.

[Mach10]

I've got an L67 sitting apart in my garage, pan off, doing the bearings.

I have serious doubts as to the power-holding capacity of a v6 block with only *4* main bearing 2-bolt saddles. Shit, even the "iron duke" has 5, and it has a reputation for having a weak bottom end