Got my project running and have a question

[zane9000]

First I want to thank everyone on here. I haven't really posted too much to this forum for a long time, but I would never be where I am today without help I have gotten over the years and the collected knowledge stored here. Anyway, I finally got my car up and running. I just drove it about 30 miles through the mountains to my house. It wasn't great, but it was way better than I thought it would be. I have a very unique set up so I will be posting pictures and asking for lots of advice in the near future.

 

For now I'll give a quick rundown of what I have. I am running an E88 manifold connected to a set of carbs to act as throttle bodies. The carbs are gutted and have a pipe running though them. On top of each pipe I attached injector holders with 1200cc RC Engineering injectors (1200cc at 55psi but I'm running 40 psi which makes them flow 1090cc). These pipes will eventually be plumbed to a Albrex centrifugal supercharger once I am comfortable with an NA tune. At the moment I have a stock 280zx turbo motor, but I will be swapping the head with a ported E88 head that has a large cam installed. I am also running MSA coated headers.

 

The question I have now is about the headers. The O2 sensor is not on the collector, but on one of the runners. Would it be a good idea to have the current O2 sensor hole filled in and a new bung installed down on the collector so I can get my wideband reading for the whole engine, or is just one cylinder better?

 

Thanks again everyone!

[Mayolives]

QUOTE:"Would it be a good idea to have the current O2 sensor hole filled in and a new bung installed down on the collector so I can get my wideband reading for the whole engine, or is just one cylinder better?"

 

Convential wisdom would dictate moving to sensor on down. Is it possable that your present location may be too hot for the sensor? I'm not sure but I'll bet that some O2 sensor guru may have a good reason to keep it where it is. I would really like to see some close up pictires of your work. It sounds interesting and very hybrid!

Edited April 24, 2010 by Mayolives

[bjhines]

I welded individual O2 bungs on each of the primary tubes ~12" from the ports and intalled 2 meters to monitor mixture. I traded the pair of O2 sensors from bung to bung to get a good idea of what was going on. I had this set up with SU carbys for a little while and then used them to tune triple Weber DCOE45s.

 

I found that the mixtue distribution with the original E88 manifold SUCKS BALLS. There are 2 cylinders that run rich, 2 stoich, and 2 lean with the E88 manifolds. I don't care how you tune them you can only shift the overall mixture lean or rich. Reading the plugs confirmed this as well, 2 plugs are black, 2 are brown, and 2 are white when you get the overall mix right.

 

The E88 manifolds just don't work very well and may cause problems for you in the future.

[Leon]

I welded individual O2 bungs on each of the primary tubes ~12" from the ports and intalled 2 meters to monitor mixture. I traded the pair of O2 sensors from bung to bung to get a good idea of what was going on. I had this set up with SU carbys for a little while and then used them to tune triple Weber DCOE45s.

 

I found that the mixtue distribution with the original E88 manifold SUCKS BALLS. There are 2 cylinders that run rich, 2 stoich, and 2 lean with the E88 manifolds. I don't care how you tune them you can only shift the overall mixture lean or rich. Reading the plugs confirmed this as well, 2 plugs are black, 2 are brown, and 2 are white when you get the overall mix right.

 

The E88 manifolds just don't work very well and may cause problems for you in the future.

 

That's very interesting insight! Did you try other SU manifolds (N36?) for comparison? I'll be running SUs when my engine is finished so I'm definitely interested if you have any other info on this.

[bjhines]

Well.. You can look at the manifolds and see how the mixture gets sent past the sharpest angled runners. The N36 is marginally better, the angles are reduced somewhat, but the 2 into 6 intake configuration is not very good at all.

[Leon]

Well.. You can look at the manifolds and see how the mixture gets sent past the sharpest angled runners. The N36 is marginally better, the angles are reduced somewhat, but the 2 into 6 intake configuration is not very good at all.

 

Good point.

 

I'd be running triples if I had a set. I suppose the simplicity of the dual SU setup comes with its fair share of compromises.

 

Thanks!

 

Leon

 

 

EDIT: To keep this on topic, I'm thinking the O2 sensor port you're (OP) talking about is really an EGR port. I don't think MSA headers come with O2 ports, but I may be wrong there. With that said, it makes sense to have the O2 located after the primaries, or else you're not getting the big picture.

Edited April 24, 2010 by Leon

[zane9000]

Alright, here is a picture of what I have done. I want to get the two throttle bodies connected to the supercharger in the bottom left of the picture.

 

 

Well that is too bad about how the E88 flows. I am hoping once I start running boost that wont be quite as big of an issue, but still...

 

My headers have an O2 bung as well as a smog port. The smog port is plugged and the wideband is installed in the O2 bung. You can see its location in the picture. I was thinking about relocating it to the collector which is just under the firewall.

 

[bjhines]

You may have another problem that will exacerbate the issues with mixture distribution.

 

You are spraying fuel upstream of the throttle plates. This will wreak havoc with mixture atomization at idle and part throttle. The condensed fuel droplets will be even more prone to following the path of inertia instead of airflow. Your O2 sensors will not be able to deal with these issues.

[zane9000]

You may have another problem that will exacerbate the issues with mixture distribution.

 

You are spraying fuel upstream of the throttle plates. This will wreak havoc with mixture atomization at idle and part throttle. The condensed fuel droplets will be even more prone to following the path of inertia instead of airflow. Your O2 sensors will not be able to deal with these issues.

 

 

yep, I realized that after it was all said and done. The initial logic was to put them where the carbs were jetting fuel, but I now understand why this is a bad idea. I will be relocating them past the plates in the near future....

 

thanks for the tip though. You confirmed what I was thinking.

[Xnke]

The injector position doesn't make that much difference. Look at the GM TBI manifolds, the injectors are all in front of the throttle plates. Millions of engines out there and they all ran fine.

 

Yes, there are more ideal solutions. No, it probably isn't that big a deal under 300-400HP.

[bjhines]

The issue is not with horsepower.. It is with drivablility. The E88 manifolds are notorious for poor mixture distribution, the current arrangement would be nearly undrivable.

 

TBI systems are different than what the poster has tried. There are several nuances to the TBI system to make it driveable(idle and part throttle mixture control).

[zane9000]

Well I have put about 250 miles on this system and it is far from undrivable. It runs rich, but I can see that each time I drive it, it is a bit better, so I guess autotune is doing its job. The #1 issue I am having with this now is that at idle with the throttle plate closed the fuel is sprayed right onto the plate, condenses, and pools. This makes my idle ridiculously rich and I have not been able to adjust the VE table to fix it. I can still drive it, but I will definitely be relocating the injectors when time/money permits.

[zane9000]

Well I have put about 250 miles on this system and it is far from undrivable. It runs rich, but I can see that each time I drive it, it is a bit better, so I guess autotune is doing its job. The #1 issue I am having with this now is that at idle with the throttle plate closed the fuel is sprayed right onto the plate, condenses, and pools. This makes my idle ridiculously rich and I have not been able to adjust the VE table to fix it. I can still drive it, but I will definitely be relocating the injectors when time/money permits.

[bjhines]

OK.. Liveability... The gassy smell at idle is typical of this problem... usually due to poor atomization from old worn out injectors. In your case it is caused by the already mentioned issue.

[zane9000]

I know, Ill just add a Vortex Valve http://www.vortexvalve.com/catalog/all.shtml . That will help, right? Hahaha

[zane9000]

I know, Ill just add a Vortex Valve http://www.vortexvalve.com/catalog/all.shtml . That will help, right? Hahaha

[Xnke]

BJhines, what zane9000 is running IS Throttle Body Injection. Yes, mixture distribution inside the manifold is not ideal. But having the injectors OUTSIDE the throttle plates is how TBI is usually done, however the injectors are normally mounted at an oblique angle to the thottle plates. In this case, I really don't think he's loosing anything.

 

To fix your puddling problem, you can either move the injector behind the throttle plate (doesn't solve the puddling issue, just moves it) OR move your injectors outward, letting them spray down the bores of the throttle at like a 5 or 10 degree angle, from about 2 or 2.5" away from the throttle plates. Either method will correct a lot of the puddling problems, but it won't solve them completely.

 

TBI has been around a LONG time, and most every implementation has the injectors firing straight at the throttle plates from outside the manifolds. GM, Ford CFI, some Hilborne, I've seen a number of F1 and similar cars rin it that way with ITB's too.

[zane9000]

move your injectors outward, letting them spray down the bores of the throttle at like a 5 or 10 degree angle, from about 2 or 2.5" away from the throttle plates.

 

That is an interesting idea. The more I look at moving the injectors past the throttle plates, the more doubt I have. It looks the If I do that it will make the distribution even worse unless I add a spacer, which I don't really have room for.

Before I put this together, I had done a bit of research and found people saying that 45 degree angle was good. That is the angle the injector holders had when I bought them, so I didn't really thing about it. I can definitely see how moving them upstream and angling them more will help atomization.

 

Thanks for the suggestion.

[zane9000]

Just wanted to update this thread. I have done a lot of work tuning the car with the injectors in the pictured location. I have been able to stop the fuel puddling and been able to hit my target afr's under most conditions. The idle is still pretty rough, but it doesn't die and fuel doesn't puddle, so it seems to be in a good spot.

 

I will probably leave the injectors in place for a while. I have bigger fish to fry right now and it runs fine.. well, fine enough.

 

Also, as bjhines pointed out, the fuel distribution is not great. However, I wouldn't say it sucks balls either. Cyl 2 and 5 run the leanest, but as luck would have it, MSA put the O2 bung on cyl 2's runner. I will leave my wideband here as to ensure the leanest cyl has enough fuel under boost.

[bjhines]

good to hear it is working. I'll be interested in how well it works with the supercharger, especially as a street car.