Newbie thinking out loud - power potential of 3.0L engines

[Ondonti]

So the real question is 5th gear. I don't see myself building a car that needs to use 5th gear when 4th gear is already too long for the 1/4 until you go into the deep 8's.

[Vigo]

Well, on the dodge trans with 5th being right next to the bearing plate i would think it is one of the stronger gears, but that's just an educated guess.

[Sundance 6g72]

I think 8000rpm is a good RPM goal for a landspeed car. I pushed my valvetrain to 8000 and everything seems fine. 3.3dodge valve springs, LS1 Retainers and locks and 270 duration cams.


Honestly, a DOHC 24v 3.0 will do well over 500whp on a good tune with easy as long as the turbo system and fuel system will support it. With race fuel, you can plan on over 700whp as long as the tuner knows what he/she is doing.

I like the 12valve for cheapness. Valvetrain parts are cheep, cams are cheep. I can get a full 12v motor for under $150 and plan on it handling my 315hp tune with ease on e85. Headflow is the issue on the 12v when going for high horsepower. Im fine with turning up my boost.. my car was just a street car though.

[Ondonti]

Well, on the dodge trans with 5th being right next to the bearing plate i would think it is one of the stronger gears, but that's just an educated guess.

There were quite a few people saying they didn't like 5th gear for strength. Probably nothing to back that up. Would not be the first time everyone was wrong! I would never want to test this as even if it was possible safety wise, 200mph winds would put a real load on the engine and I would never need a tune that was safe at 200mph brick wall of air speed. I do tool around a lot with 5th gear and boost but thats not a racing gear for me. Street racers probably get more into that gear.

Is this a salt flat car or what? Kinda far away. I never even visited when I lived in Utah

[Jetmugg]

Yes- this is a purpose built Salt Flats race vehicle.

[Reaper1]

My only questions about using 5th for a lot of power are: the gear strength themselves and the actual shafts. That gear hangs off the shafts on the very end. I've got the personal goal of hitting/sustaining 200mph+ in my car (not trying to break records, I just have the goal for myself and the car) and have always calculated it used 5th gear and then using tires to alter the FD without having to get super expensive using custom gears. My rpm ceiling I put in for myself is 8000 with engine redline at 8500. If I can get it lower, that's even better. I'd rather not have to rev the engine that hard.

[Jetmugg]

Agreed - my Rampage is currently using a VW / Dodge Omni 4-speed transaxle. There is an overdrive 4th gear that matches the overdrive 5th in some of the later transaxles. The designs are similar to the Dodge transaxles, in that the 5th gear is basically an "add on" gear to the end of the shaft. Talking to my transmission guy, he felt that the 4 speeds were much more durable. The biggest issue is that the 4 speed is a much wider ratio trans than the 5 speed.

[Reaper1]

The VW 4-speed has the 4th gear outside of the case? I thought they were contained within the case? Which VW tranny again? I just want to look at it for myself for curiosity/educational purposes.

[zin]

I think he was referring to the 5-speed VW transmissions, not the 4-speeds... The confusion may be in that he also mentioned that there was an overdrive ratio for 4th that was the same as that in the 5-speed, but that it made for a very wide ratio 4-speed.

Mike

[Reaper1]

Man, I hate to say it, but I'm still confused! LOL

[Ondonti]

Man, I hate to say it, but I'm still confused! LOL

Sounds to me more like that the 4 speed had an option to bolt on a 5th gear (overdrive) but since the 4 speed has wider gear spacing (not intended to have a 5th gear) you don't need 5th gear in power situations.

I volunteer to build a car and Reaper can do the 5th gear testing :P I think half the car will be torn off since I won't build it for completing the high MPH test :P

One hard thing is that you need a big turbo high rpm setup to really require 5th gear and that means you have to be going really fast just to put a decent load on it. I figure 4500 rpms min for a lot of setups to start peaking torque and thats 130mph to start :P

[Reaper1]

Sounds to me more like that the 4 speed had an option to bolt on a 5th gear (overdrive) but since the 4 speed has wider gear spacing (not intended to have a 5th gear) you don't need 5th gear in power situations.

I volunteer to build a car and Reaper can do the 5th gear testing :P I think half the car will be torn off since I won't build it for completing the high MPH test :P

One hard thing is that you need a big turbo high rpm setup to really require 5th gear and that means you have to be going really fast just to put a decent load on it. I figure 4500 rpms min for a lot of setups to start peaking torque and thats 130mph to start :P

That's how I interpreted his description of the 4-speed...that it had the option of bolting on a 5th gear just like our transmissions.

Brent, if we tear off half the car, then the load will be different! LOL Maybe we build a van, load it with crap to make it really heavy, then load it down to test 5th. We could put really small tires on it so we don't have to be going a million mph to get in the upper rpm's in 5th.

Sound like a plan? :deal: