LudeRage

I won't flame...I won't flame...

The only thing you rougly pointed out was that an LS motor is far superior to an EX motor. I really wish I could transfer everything from my LS over to a CRX or hatch and still have 2 cars! Grrrrrrrr.....

I just can't decide what to do. I'm pretty solid on leaving my LS as is, and keeping it as my daily driver just so I have a dependable daily driver. So I just need to figure out what to do as far as a hatch project goes....

So far I really like the d16 turbo hatch idea. But how much harder would it be to put an LS motor into a hatch? I've seen a few guys with it; doesn't seem like any hard modification, and I know you can get 90-93 teg engines for pretty damn cheap. That would put down way better numbers than any d-series engine too. Suggestions??

v8guy

Seriously, what good is VTEC going to do you with a turbo? VTEC grinds are not all that turbo compatible. Why even bother with it? Thats why I suggested picking up a dirt cheap LS engine and spending your money on the turbo setup. A D series swap would be easier because you won't need custom mounts and that would work as well. As for the LS swap, from what I understand it is really no different than swapping in a B16A except you don't have to wire up VTEC. I know there are turbo VTEC cars out there, I'm not saying it can't be done, but VTEC is a NA game and is not really suited for FI.

augy

v8guy is right on this one--you're much better off just saving the vtec money and putting it towards your turbo. Kai has pointed it a number of times that all vtec does is save you the inconvenience of a lopey idle and probably (though I haven't seen dyno charts) some loss of low-end torque from the adjusted valve timing. If you really want the max at the top end, just buy adjustable cam gears and you can get nearly the same performance.
Also, check compression on the LS engine. I don't know the stats on it, but if it's too high (vague, I know, but I don't know much about the LS engine), then you're going to have to invest significantly in the internals to make it withstand anything more than a daily driver level psi. I suggested the ZC because it has low compression and compliments a turbo approach extremely well. Check out homemadeturbo.com; those guys seem to use ZCs almost exclusively, so there's a lot of documentation on the procedure.
Be wary; there is a SOHC and a DOHC ZC. If you want to adjust valve timing like I suggested, you'll want the DOHC version.

LudeRage

LS motors have low compression, 9.5:1. Either way, I was going to put forged pistons and rods in whatever motor goes in so I don't have to run 5 psi like the 15 second Greddy turboed Civics. I'm looking to run close to 15, as it is going to be primarily a track car, and there are numerous d16 turbos on www.turbod16.com, that have huge amounts of horsepower on the stock head with a built bottom end.

The problem with the LS swap is that I would need, as you said V8 guy, different mounts and I believe different axles also. So it would be more costly and more work, and I'm really just looking for a cheap project (which will still be fast).

A ZC doesn't sound like a bad idea, but I was planning on looking for a 92 hatch so an EX motor would go right in, plus be OBD-1 like the car. I'm still pretty set on the EX motor.

As for VTEC only being for N/A...I disagree with that. I'm not sure what kind of information your basing that on. All I know is that a GSR motor with a few less psi still makes significantly more power than an LS with the same set-up. And I'm sure an EX motor makes more power than a DX motor, too.

Edit: It's www.turbod16.com not www.d16turbo.com, sorry.

augy

Well, we weren't saying that vtec is ever bad for turbo, but it isn't worth it's price and it sounds like you are on a budget. But hey, if you're willing to spring for it, you'll do just fine

and at 9.5:1, the LS has enough room for boost, and with upgraded pistons/rods, I think you get get more than 15 out of it.

pillz

u need sleeves too

twin3037

vtec does help turbo cars now for the extra money it's not worth it in this case. If your going to run the same psi then a higher compression motor will make more power then the lower compression

v8guy

I was going to recommend turbod16, thats a great site. I don't think anyone is saying you can't use VTEC with a turbo, obviously there are plenty of quick turbo VTEC cars running around. What it comes down to is cam design. Turbos don't like a lot of overlap and high-rpm NA engines do. I understand this mismatch can be compensated for somewhat by the use of adjustable cam gears, but it is still not an ideal situation for a FI engine. VTEC is a NA game. I don't have the time to write a mini-book on cam design and airflow dynamics not to mention general engine operation principles, but basically cams that produce great top end power suck ass for forced induction. The reason is rather simple. When engine RPMs increase, the intake valve needs to open earlier and earlier in order to allow enough air in to fill the cylinder. Consequently, overlap increases. Overlap is the number of degrees of camshaft rotation during which both the intake and exhaust valves are open. So what we have is the intake valve (or valves) beginning to open while the exhaust valve is closing. In a NA engine this is useful because you get a scavenging effect. The momentum of the exhaust gases leaving the cylinder helps pull in the incoming intake charge. This is how it is possible to build NA engines with volumetric efficiencies greater than 100%. However, this situation sucks for FI because what happens instead is the pressurized intake charge does an abrupt about-face and heads right out the still-open exhaust valve. Sound :ghey:?, well it is. Very :ghey:. In a nutshell, this is why VTEC isn't all that well suited for FI applications.
As for your GSR turbo vs LS turbo comparison, there are a lot of other variables to consider besides VTEC. Off the top of my head I would venture a guess that transmission gearing would give a significant edge to the GSR, especially if it had a LSD. Another thing I would like to point out is that if we take two engines of identical displacement and fit them both with identical turbochargers, it is entirely possible that one could make more power at 10psi than the other does at 15. To see why this is try blowing through a drinking straw. Then try blowing through a section of garden hose of the same length. It takes a lot less pressure to blow through the garden hose now doesn't it. It takes much less time to blow a lungful of air through the garden hose than it does through the straw as well. Now try and translate this to a turbocharged engine. A turbo blowing through a restrictive intake manifold and cylinder head is going to produce a higher pressure than a turbo moving the exact same volume of air through a better intake and head combo. So a higher intake manifold pressure is not a sure sign of greater power.

One thing I would like to add is that it would seem to me that the VTEC principle could be useful for FI if VTEC merely increased valve lift without increasing overlap. Custom cams would do this, and and adjustable cam gears can be used to pull out some of the overlap from the stock cams, but obviously this is not the ideal situation. However this is all way beyond the scope of a budget buildup, which is why I said to forget about VTEC in the first place and save your money for something else.

v8guy

Oh, and yeah a D series swap would obviously be the easiest. If I was going to turbo my CRX I'd just use the D16A6 thats in it right now. The LS engine would be a better starting point, which is why I suggested using it. Yeah you would need custom mounts, but how great do you think your old mounts are after all these years anyway? You would need a matching tranny and axles to go with the B series engine, but from what I understand there is an advantage to running the Integra axles over the civic axles anyway. This sounds like the way to go to me. Good luck with whatever you decide to do.

LudeRage

Hey thanks alot man. Good info. Yeah I was going to go with the EX motor just because they're dirt cheap anyway. I agree that an LS is the best way to go, and even getting integra axles isn't a problem considering I would have replaced the civic ones down the road (after they broke).

So really I just need the motor, stage 1 integra axles, ecu, mounts and shift linkage. Sounds like a plan!