Jump to content

Weber 45's vs 50 or 55 dco/sp's


scooter

Recommended Posts

On the quest for more power out of my lz23, on the intake side im using a ported cannon intake with 45's with 40 mil throats. Right now it tapers off around 7000rpm, but when its on the bottle it pulls hard as fuck to redline with no reduction.

 

Would it be beneficial to run 50's or 55's? Will i see more power in that last 1500 rpm?

 

Is the intake a bottleneck?

 

Also looking for feedback on how the large webers drive compared to the smaller ones. Right now the cars fairly driveable, it doesnt like to be grannied and comes on hard at 4 grand or so.

 

But if a policeman is behind me, i still want it good enough to leave a stop sign composed

  • Like 1
Link to comment
  • Replies 18
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

On the quest for more power out of my lz23, on the intake side im using a ported cannon intake with 45's with 40 mil throats. Right now it tapers off around 7000rpm, but when its on the bottle it pulls hard as fuck to redline with no reduction.

 

Would it be beneficial to run 50's or 55's? Will i see more power in that last 1500 rpm?

 I don't have experience with performance in motors...but obviously your forcely induced nitrous pushes your motor to redline with no hesitation, therefore your carbs or intake aren't cutting it to where you want it lol. My guess would be not being able to suck air efficiently enough. If you think of it, the side drafts are sucking air perpendicular to the moving air. I'm guessing you're running air horns tbh haha

 

Maybe try a custom intake to flow air to the carbs ...and you'd probably have to run dry shot or something like that?

 

It honestly sounds like your intake/air flow is the problem, if you want more power off the bottle. Damn let me drive your car. My baby l-16 can't even pass 4k!!

Link to comment

How big is the cam? Is the head ported? What is your compression ratio? Aluminum Flywheel or Steel? And so on.........

Cam is .530 lift 274 at .050 head is ported with 45mm intake and 36mm exhaust, 12.3:1, flywheel is a 225mm with the back turned down so its about 15 pounds or so.

 

Had a shitty ebay header on it that didnt match the head at all, now it has the niscomp/dp racing header that is properly port matched.

 

2.25 inch pipe all the way back.

 

The intake probibly could get hogged out a little more, its a lil tight where the nitrous nozzle is, i can get a finger on either side of the nozzle in the port but its definitely tighter there than on the carb side.

Kinda thinking 55's with 46 mill throats would help the midrange and the top end, but it might get boggy too.. Hmm

 

I don't have experience with performance in motors...but obviously your forcely induced nitrous pushes your motor to redline with no hesitation, therefore your carbs or intake aren't cutting it to where you want it lol. My guess would be not being able to suck air efficiently enough. If you think of it, the side drafts are sucking air perpendicular to the moving air. I'm guessing you're running air horns tbh haha

 

Maybe try a custom intake to flow air to the carbs ...and you'd probably have to run dry shot or something like that?

 

It honestly sounds like your intake/air flow is the problem, if you want more power off the bottle. Damn let me drive your car. My baby l-16 can't even pass 4k!!

Have you seen a datsun out pull a "stage 3" sti? Buddy of mine has an evo x with a pile of bolt ons and he aint pullin by much.

Although the front fenders have nearly ripped off the car a couple times from highway pulls.. Because ratsun

  • Like 1
Link to comment

The 'chokes" (main venturis) are too big, try 36's. Your port velocity sucks.

I tried this, had more bottom and mid range, but it felt like it had less on top according to my butt. I could try this again as it was a couple years ago now.

 

Should probibly run it on a real dyno, in case my butt dyno is wacky or something.

Link to comment
  • 3 weeks later...

I highly doubt anything bigger than DCOE 45's are necessary.  I'm putting 50's on mine, but it'll never ever see street use.  If your power tapers off, I suspect the fuel mixture is incorrect, not a lack of carb size.  Either get an AFR on it or spend an hour at the dyno.  It may just need different air correctors.  Yours are likely too large if adding more fuel makes it run better.  

By the way, adding 50 mm DCOEs is a massive undertaking.  Porting through the manifold and into the head is necessary.  I assume you ported your head, more than just a gasket match to the Weber manifolds?  

Link to comment

Why not R-1 constant velocity carbs on a custom intake? Straight line for the air flow, individual carb per cylinder, no bends and you can' tune' the lengths as well.

 

Redline for a stock Z22 crank/rods/bolts LZ23 is 6,500 RPMs. This is a piston speed of just barely under 4,000 feet per minute above which strains the metal to stay together. I haven't looked to see what you've modified on this engine and I'm not saying you can't rev higher but it's ill advised to hold it above this 'redline' using factory rod bolts and rods.

 

 Have to say I'm looking forward to seeing this car at Canby.

Link to comment

This is essentially a full built race motor. The only lame thing I did that I would like to change is it has shot peened l20b rods with arp bolts in them. On nitrous I'm probably at the max of what these rods can take, but at the same time I've ran about 5 10 pound bottles of nitrous through it at a 75 shot. A few times it was long highway pulls too. I have put a different header on now that's port matched so I'm certain that will make a difference. The previous header was really really shitty. I'll post an oic on how bad it was later.

 

I'll check out the Pierce manifold setup, but I'll probably hold off to see if it picked up any up top from the header.

 

I usually don't turn it more than 7000 but occasionally it gets to 7500 (Rev limiter).

 

The head and intake are ported, when I had the wideband on it, its was in the low 12's down low and would climb to about 12.8 sometimes would flash 13 up top.

 

I might try putting a smaller air corrector in it to fatten it on top. Something I'll have to play with when the snows gone.

Link to comment

This may have been a cause. The gasket is cut to match my head and new header, but this is the old header underneath. As you can see the port match was REALLY BAD. The header had even tinier ports in the flange when i bought it, it was welded from the inside. I re welded them from the outside and then attacked it with a die grinder so it kinda flared the flange into the tube. This is the shitty racetep header or ebay header. The new header matches the gasket perfectly and has larger primary tubes.

 

This header is probibly worse than running a manifold, but i didnt have a manifold so i bought this. Now it has a dp racing header on there.

 

The white crusties is from leaded gas ;)

 

IMG_20170126_1824138_zpsyyikm9nt.jpg

Link to comment

If you want to play in the 8k range, header tubes will need to be in the 1 3/4"-1 7/8" range.  Hopefully your new header has ports larger than that gasket?  My Bonneville truck header has 2" primaries with the goal of exceeding 9K if needed.  Your I/E airflow in the head will need to be in the mid-90% range to get rpms, and your cam needs to be retarded which will lose some low end power.  

  • Like 1
Link to comment

If you want to play in the 8k range, header tubes will need to be in the 1 3/4"-1 7/8" range.  Hopefully your new header has ports larger than that gasket?  My Bonneville truck header has 2" primaries with the goal of exceeding 9K if needed.  Your I/E airflow in the head will need to be in the mid-90% range to get rpms, and your cam needs to be retarded which will lose some low end power.

 

The new one is slightly larger than the gasket. But as you can see the one i had on there was signifigantly smaller. The header,gasket and head actually match very well now which should help. im not looking to turn it more than 7500 for connecting rod integrity issues, but you could feel it starting to fade the last 1000 rpm.

 

The new one is 1 5/8". The old one was inch and a quarter or inch and a half or something. Looks like a hunk of shit compared to the new one. Troy ermish is selling really nice stepped tube ones with a merge collector but 1600 us for a header is too much for me.

 

I did have the cam a little retarded but then i decided to try it straight up and it dropped the powerband down a bit. Feels like it comes on 300-500rpm sooner.

Link to comment
  • 1 month later...

DCOE50's aren't needed until you start turning 9-10KRPMs. The 45's are fine.

 

The 40mm chokes probably could stand to be 42's, but it'll start going to shit on the bottom end as you get closer to 48mm chokes.

 

Also, 50DCOE's do not fit the same manifold as 45DCOE's...just so you know.

 

L20B rods with good rod bolts will be fine until 8000RPM/260HP. Until you hit those, don't worry about the rods.

 

Butt dynos are notoriously inaccurate, they are strongly affected by aural interference.

Link to comment

 

 

Also, 50DCOE's do not fit the same manifold as 45DCOE's...just so you know.

 

 

45DCOE manifolds can be used for 50's, but I can vouch that its a hell of a lot of work!  Welding inside and out, porting to match and straighten airflow.  Modifications just so you can mount them after all that.  

Link to comment
  • 1 month later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.