3.4 DOHC powerband what would you change? top end build qs.

[mr_merkur]

Well as you prolly know my buddy and I are doing up a turbo 3.4dohc for his z34. We are shooting for the broadest powerband possible and making it responsive as hell . Unfortunatly neither of us have riddin in a 3.4DOHC car so neither of us know what its about. How well are they for low end torque? I'm going to make a custom intake manifold with what were thinking maybe 3 throttle bodies (1 for ever 2 cyl ). Just I'm wandering if we should design the manifold to give us more low end torque or shoot for a higher end power. Do these engine have a tendancy of running out of steam quick or what? I was thinking making short little fat runners, although the factory ran long runners. My Idea was to run the 3 TBs about 21/22mm a piece, facing strait up or facing backwards, then using a round pipe (large of course) to connect all three TBs (sort of like they do on my crotch rockets. then have the the intercooler piping go srait into the pipe.

What other GMs came with about a 18-22 mm TB give or take, does it have an adjustable TPS?

From research all I've seemed to find is that there are no other cam options for the 3.4dohc unless we get a custom regrind wich nobody has done to get any experience, and not sure if we wanna dump that kinda money into a guess just yet.

opinions, comments and other b/s welcome, sorry for all the questions though, just dont wanna waiste money, time and effort into junk.

[99RegalGS]

IMO if you want more lowend just use the 91-95 Intakes. It has long narrow runners (better for lowend).

[slick]

Yep, go with the 91-95 intakes. You will have more low-end than pretty much any of the other 60*'s on this board, except the Turbo 3.1.

 

I would suggest messing with the timing some as well. Actually, your gonna need to. If your not looking for a high rpm rever, say 6500 you set as redline for yourself, be sure to choose a turbo that would start to kick in around 2500-3000 rpm, look for peak around 5500 rpm, and hope that it would be done and over around 6300 rpm.

[z34Phoenix]

i thought that on boosted cars, the runner lengths didnt mater? as long as they all were the same lenght. i know a kid that is trying to adapt a m90 for a DOHC. i too am thinking up a new Intake system to accomidate either m90 or a lower profile intake for boost. i'll be getting pics up once i get a design for somthing that should work. I'll keep all posted

[DaveFromColorado]

even on boosted app's, runner length does matter, it'll effect your torque curve quite a bit - however, most people with boosted app's don't care about low end torque, so they open the runners up as much as they can to get the most effective pressure across the whole engine.

 

there's a whole set of calculations for this.

 

--Dave.

[mr_merkur]

and see thats what I'm trying to figure out if we should design it for more low end grunt or top end mean-ness so we get a nice broad powerband between the turbo and intake . I'm a firm believer that an intake makes or breaks the engine. Youve got to design an intake with a certain RPM range in mind, then you do some crazy calculations using air speed etc. because when your intake valve closes the extra air bounces back and hits your TB then bounces back and you want it to hit your valve at just the right time for best results, if it is sligtly too long or too short the air pulses wont match up and cause a loss of performace for that RPM range.

The reason I was thinking Fat runners was for more air flow in the higher RPMs (If the engine has a tendancy of running out of steam soon) but the shorter runners for the small area and yea. I'm gettin tired haha. I can go more in depth if need be.

[DaveFromColorado]

go for top end all the way...

 

Just like the turboford guys gut out the intakes, I was thinkin' about doin' that on this DOHC engine ... even leaving it N/A and gutted out I'd imagine on a turbocharged engine, this would make some seriously high rpm power.

 

--Dave.

[mr_merkur]

I might just have to try that on the extra manifolds we have . I'm glad I have a small fortune in carbide burs

[95oldsVan]

Is it at all possible to put a turbo set up in that engine bay?Looks severely cramped in there.

[DaveFromColorado]

it's been done a few times already.

 

--Dave.

[mr_merkur]

if i can put a turbo v8 in a merkur a turbo in a z34 is possible

[joey b]

How well are they for low end torque?

 

I think that is the main question you are trying to get at. As for low end torque, the 3.4 sucks. Don't get me wrong, you might be able to get a nice sqawk, but if you have an auto that is all you are gonna get cause you can't just pop the clutch out like a manual. As far as power, the stock NA 3.4 has very little below 3500 RPMs. Between 3500 and 4K it kicks in and gets its highest torque reading at 4200, which is a tad high if you have an automatic. I would definately shoot for some lowend power if I were you, or else get a manual put in.

[TeeJay3800]

IMHO, the 3.4 doesn't have shit for low end. Trying to get bottom end out of a 3.4, is like trying to get top end out of a 3.1.

[fastbird232]

It's got more low-end than a 3100...

 

(and I'm basing that off a race with a '00 SE, where it wasn't even close off the line)

[gp90se]

my 3.4 will smoke the tires clear into 2ed gear with a 4t60e.

[Prospeeder]

Ahhh another the 3.4 has so much low end, i can roast them all day long, and the other people say the 3.4 is dog slow down low with no power thread...everyone knows my take on it...

[digitaloutsider]

Yet no one cares about your opinion since you've never owned, let alone driven an LQ1 powered car.

 

[Hammers in a "Don't Feed The Troll" sign]

[gp90se]

hey prosped, PM me, ill end you in there, quit brining your stupidity all over the board

 

The bottom end of a 3.4 is not bad for a dohc motor when N/A but when tuning it for a turbo, you are going 2 want to put in a little timing, which might hurt the bottom end, but will be made up for with that hairdryer install

 

BTW, my turbo 3.1 and 3.4 dohc had about as much bottom end as each other, but since I have not been able 2 really drive the 3.4 yet, I cant tell ya about the top end power of it.

[mr_merkur]

well we already have the 5 speed . so I guess were gonna shoot for

[Prospeeder]

hey prosped, PM me, ill end you in there, quit brining your stupidity all over the board

 

The bottom end of a 3.4 is not bad for a dohc motor when N/A but when tuning it for a turbo, you are going 2 want to put in a little timing, which might hurt the bottom end, but will be made up for with that hairdryer install

 

BTW, my turbo 3.1 and 3.4 dohc had about as much bottom end as each other, but since I have not been able 2 really drive the 3.4 yet, I cant tell ya about the top end power of it.

 

Your 3.1 turbo was a heap of shit, poor gutlass supreme got ahold of that heap of shit you beat the hell out of

[jeremy]

Yet no one cares about your opinion since you've never owned, let alone driven an LQ1 powered car.

 

[Hammers in a "Don't Feed The Troll" sign]

 

 

at least he is gone for a while now....

[fastbird232]

LQ1 has plenty of low end. I think someone on here said if you compare the torque curves of any Gen-1 engine, the LQ1 is the highest at any RPM. I'd believe them, having driven all the motors (all except the 3.1 turbo, which I couldn't speak for).

 

I think there's a common misconception on this board that the pushrod engines all have better bottom-end than the LQ1. We need to put this one to bed with some HARD GODDAMN PROOF one way or the other.

[DaveFromColorado]

here's my take on it...

 

3.4's that have had the shit beat outta them have NO low end, 3.4's that have been taken care of have enough low end to be happy, and ALL 3.4's have good high end power.

 

You can tell if you have a 3.4 that's been beat on, because you'll assume they all have no low end because it'll still fly on the high end, you can also tell if you have a good 3.4, because you'll pay more money for it, or it'll come with lots of body damage (like my car)

 

I burned through a set of good tires in one summer - if I didn't have any low end, this wouldn't have happened. of course, this could also be why my trans. blew up.

 

--Dave.

[JakeMetz63]

My LQ1 has less than 20k miles on it, and it has more lowend than my 3.1 did. I would definately want more bottem on it than it has, the 4T60e was really never meant to be paired up with that engine.

[mr_merkur]

so this helps confirm Dave's beliefs on the torque. . . hmmm. could it be the timing belt streaching causing the loss of low end?