BSR GTU E31 Head Images

[josh817]

Ahh I understand now. So I guess either extremely large, EFI, or... perhaps mechanical injection. I've seen some mechanical injection systems but they all show a full throttle best running condition, so that would be comparable to carbs with no chokes I'd assume. This time instead of going lean, you would go rich I think. I've always tried to avoid the other side of the tracks, EFI, for me. I'm sad but shouldn't be surprised that they run better. Lol

[z-ya]

Choke tubes = venturis. If you remove the venturis from 44s they become 44s, which is the diameter at the exit hole of the carb. No change you make to the venturi is going to change the size of the exit hole. The venturis neck down the opening to speed airflow through the carb at low engine speeds. I believe Mikuni shipped most street bound 44s with 34mm venturis.

 

Todd at Wolfcreek said that they were ported downstream of the throttle plates to match the intake manifold. Maybe that is where he got the 50mm from? He said there is no going back to 44 at this point. I know nothing about these carbs (leaning).

[z-ya]

Ahh I understand now. So I guess either extremely large, EFI, or... perhaps mechanical injection. I've seen some mechanical injection systems but they all show a full throttle best running condition, so that would be comparable to carbs with no chokes I'd assume. This time instead of going lean, you would go rich I think. I've always tried to avoid the other side of the tracks, EFI, for me. I'm sad but shouldn't be surprised that they run better. Lol

 

Avoid mechanical injection. You are building a street car, right? I'd go with triple ITBs and EFI. Port the manifold to match the bore of the ITB. That should be more than enough air flow for the application. The only reason I am going with Mikunis is because of vintage racing rules. I've got EFI and dual 50mm TBs on their now, and it runs great. Great throttle response.

[JMortensen]

Todd at Wolfcreek said that they were ported downstream of the throttle plates to match the intake manifold. Maybe that is where he got the 50mm from? He said there is no going back to 44 at this point. I know nothing about these carbs (leaning).

Not sure what that means. Most of the carb bodies taper from the air horn to the manifold side as Tony said. The stock 44's have an opening on the air horn side of 48 or so IIRC. The size that determines if it is a 40mm or a 44 or a 50 is the manifold side.

Edited October 14, 2010 by JMortensen

[josh817]

Avoid mechanical injection. You are building a street car, right? I'd go with triple ITBs and EFI. Port the manifold to match the bore of the ITB. That should be more than enough air flow for the application. The only reason I am going with Mikunis is because of vintage racing rules. I've got EFI and dual 50mm TBs on their now, and it runs great. Great throttle response.

Not for the street. I have it registered as an antique so that when I do something I can test drive it. Its going to be a track only car and I will find a club to run it in. Now that I'm looking at mechanical injection though, it looks even simpler than carbs but thats because it doesn't offer all the things carbs do. I'm going to do more research on whether the car would run... worse than horribly when part throttle. I've seen cars at the track in vintage that run and kinda sputter when going through turns but still do great as long as they can get on the throttle well without any bogs.

[z-ya]

Not sure what that means. Most of the carb bodies taper from the air horn to the manifold side as Tony said. The stock 44's have an opening on the air horn side of 48 or so IIRC. The size that determines if it is a 40mm or a 44 or a 50 is the manifold side.

 

I don't either, as I don't know sh*t about these carbs. All he said was that the venturis were removed, and they were bored to 50mm. Oh yea, then he said don't bother trying to use them on your 200HP L6 as they are way too much.

[JMortensen]

There is a little bit of discussion about hogging the 44's out in the How to Modify book. That must be what he's talking about, but if they were bored out then the opening at the manifold side would be 50mm or thereabouts.

 

That's quite the cool pile of parts you picked up. How did that all come together? (separate thread?)

Edited October 15, 2010 by JMortensen

[z-ya]

There is a little bit of discussion about hogging the 44's out in the How to Modify book. That must be what he's talking about, but if they were bored out then the opening at the manifold side would be 50mm or thereabouts.

 

That's quite the cool pile of parts you picked up. How did that all come together? (separate thread?)

 

Todd was pretty anxious to get his hands on them (did you sent them yet?, did you send them yet?). He's going through them and setting them up for the new engine I'm building.

 

Yes, we got quite a bit of stuff. I'll start another thread with the story.

Edited October 15, 2010 by z-ya

[josh817]

Sorry... I kind of raped this thread. :[

[HowlerMonkey]

On rotary engines, Weber 48IDA were popular carbs and many racers ported the venturis and throttle plates to 51mm or so.

 

The caveat is that you lose a bit of the "signal strength" that is created by the venturi if you change it's size or countour.

 

Rotary guys already have low rpm response issues that require a rev happy driving style so the lack of signal is just a drop in the bucket on a J-ported, monster ported, or peripheral ported rotary.

 

These are downdraft carbs but the same principles apply when enlarging.

 

If you want to see extremely large ports, you should take off the plastic plenum of a lexus IS350......pretty amazing.

 

You can look down holes that are near 50mm or larger and see about 98% of the valve where it touches the seat.....the runners are that straight.

Edited October 16, 2010 by HowlerMonkey

[Tony D]

Now that I'm looking at mechanical injection though, it looks even simpler than carbs but thats because it doesn't offer all the things carbs do. I'm going to do more research on whether the car would run... worse than horribly when part throttle. I've seen cars at the track in vintage that run and kinda sputter when going through turns but still do great as long as they can get on the throttle well without any bogs.

 

Lucas slide valve injection or Hillborn is a vailable and can be made to be relatively tractable for the street (Lucas moreso than Hillborn) but if you think this will be 'easier' than carbs, under the same assumption that carbs are 'easier' than EFI, you are sorely mistaken. In both cases.

 

I'll remind you that 240Z's had EFI in competition as early as the RAC Rallyes in Europe 1971 or 72. 45mm ITB's with 'Nissan' on the base and the Nissan Competition Manifold same as on the 44's. Run through a JECS CPU that looked surprisingly like a 68 Volkswagen Type 3 Box...

[josh817]

I'm not here to bash other systems and I know you're just saying that to correct my logic of simplicity, but I just feel uncomfortable with EFI and I am becoming very fond of this MFI idea. One thing may be easy for you but hard for me to get. This MFI is clicking, webers kind of clicked, EFI is completely unknown (thus the fear of the unknown). Not worried if it sputters and **** on the street. The only reason why it would be on the street is for a test drive or driving to a club meeting or something.

Edited October 17, 2010 by josh817

[Tony D]

Ecactly what 'clicks' about Mechanical FI that in concept is any different than EFI?

 

Alpha-N EFI runs on throttle position and engine speed--same as MFI, save the components are a buttload cheaper and you only buy injectors once... The people who ding the EFI for it's drivability issues when set up that way would ding the MFI for the same.

 

Setting up EFI for Alpha-N is FAR easier than any multi-mapped setup.

Edited October 17, 2010 by Tony D

[josh817]

You're not going to let up until I go EFI.

 

I'll see. I've heard of Hillborn systems converted to EFI. Must the injector bosses be welded on the flange spraying into the port or could they spray into the runner, close to the port, where the normal nozzle would be?

 

Conversion with screw-in injector bungs for EFI is the plan.

 

Inform me on here or in a PM maybe?

Edited October 18, 2010 by josh817

[Tony D]

Most high horsepower injection systems inject at the air horn. Making a bridge to hold the injectors is simple with some aluminum a drill press and some screws. If you have a fuel rail section, you are set up to make an F1 Style injection setup out of just about anything with a throttle bore on it.

 

People decry "TBI" but go take a look at every F1 Engine out there, and what most Hondas/Mazdas/Toyota/Etc are now doing with their ITB's!

 

 

Injectors in the middle of the air horn. Great atmoization, and plenty of time for homogenization of the mixture down the intake tract.

 

The earlier comment was in response to Hillborn supposedly having conversion fittings for their existing injection setups to convert to EFI. No welding needed. The adapters screw in to the original holes for the mechanical injection nozzles, and allow the EFI injectors to be positioned there. For the bent manifold, this may be problematic due to proximity to the header. Heat shielding may be in order. They have since stopped offering this stuff, though BDS does offer a conversion 'package' for older manifolds. The Stock EFI stuff on the rally cars injected through bungs that put the injector midway on the 'carb body' and injected just after the throttle plate near the ITB/Comp Manifold Juncture. Still quite a ways upstream of the stock EFI manifold and it's emissions-dictated back-of-the-valve requirements.

Edited October 18, 2010 by Tony D

[BLOZ UP]

Dude, Josh.

 

You should go EFI.

 

Megasquirt for the win!

[josh817]

I've seen the spraying down the air horn (I guess its called TBI? woops! stand off injectors) but I see in your picture there is a second rail of injectors after the throttle plates. Is that for idle? I see that sort of setup being hard to make an airbox. I'd like to filter my air. I'll do some research before I say anything. Like I said before, I know nothing about injection at all.

 

Edit:

For the past 3 hours I've been looking over EFI MS stuff. I'm sweating.

Edited October 18, 2010 by josh817

[RIP260Z]

Josh,

Conversation moved on a bit since you asked...my Rebello is a street application.

 

On post 19 you mentioned a 45mm bore and at the front, there is a step making the carb bore a little bit bigger. If I remember correctly, this is for an o ring to sit in so there is a nice air tight fit for the air horn/trumpet to sit on.

 

just info here....You mentioned you like to stick to Webers 'cos you know them, but the same type of jets are used (e.g names), just a different way of numbering the sizes for Dellorto, and probably for PHH's as well.

 

Cheers

Ian

[Tony D]

Making excuses won't make it happen. The building of an air filter or airbox will be equally as difficult on a carburetted car as one with injectors shooting down the former carb throats.

 

If you can picture this, standard Bosch Injectors of 550CC size mounted inside the stock 73 Flat Top air cleaner supplied and regulated (with a 280ZX stock FPR INSIDE THE AIR CLEANER ITSELF!) without any untoward perforations noticable to the casual onlooker.

 

If that can be achieved, punching two holes in the back plate of an ITG air fliter for fuel in and fuel out doesn't seem all that difficult.

 

The secondary injectors on there are because TWM is mounting supplemental injectors for higher rpm usage. Or for methanol injection. Or for whatever reason. I know people with a set of 370CC injectors at the head which runs from idle to 3000rpms. Another set of 550CC injectors that run from 3200 till fullboost and to around 6000rpms. Both sets shut off at 7000.

 

That's when the third set of 1100's kick in for the trip to redline.

 

TWO computers, one controls the first two sets, and the third runs a totally different computer which is totally RPM / Boost / Throttle Position based. Ignition timing is handled by the first computer through the whole RPM range.

 

And you're worried about throttle position and rpm based fueling only? It's entering (on a megasquirt) values on an 8X8 matrix. 64 bins. 144 if you choose the 12X12 bin setup. It's far easier than you think it is...

 

If you let your fear limit you, you will remain limited!

[josh817]

I think I'm starting to get it. I just freaked out a little looking at the setup section of the forum. All sorts of terms I didn't know but I have a feeling its explained a zillion times somewhere on the interwebs. The air cleaner thing was easy to me for carbs cause I already had an idea! lol I'll need to get better pictures/get my hands on the manifold I want to use, and eyeball it while I ponder.

 

I wouldn't run triple injectors because of the cost ahh! I get the idea of doubles. I read things like large injectors are hard to control at low RPM, so you run the smaller set like you said for lower RPM and switch to large ones after a certain point. For my N/A application, my largest injector would be 450-ish I think I saw, for a 3.1L 8000RPM max therefore I wouldn't need 3 injectors since the gap between my smallest to the biggest isn't that big...? I also read that they use two to switch over at higher RPM's for the atomization. I'm wondering if I can run just 1 set but mount them outside the trumpets or whatever. I don't see that working though when the butterflies are closed. This would help save money on double sets and on having to have someone weld bungs onto the runners. If the runners are Mg then I don't even know.

 

Luckily one of the Megasquirt things has a staged injection setup if I have to go with 2 sets. Don't know if its MS1, MS2, or MS Extra.

Edited October 19, 2010 by josh817