intake design Q

[Tony D]

I should have stopped by that week after New Caledonia!

[ozconnection]

I should have stopped by that week after New Caledonia!

Yep...and not even a call you're not comin over. 

Edited January 10, 2013 by ozconnection

[ozconnection]

Really, using the 4bbl manifold and TBI isn't going to gain you *much* more than a "perfectly" setup carb would...that is, you would be dealing with the same issues of charge robbing and unequal runner length. You'd gain better precision control over the fueling, and easier precision tuning over a carb, but other than that it'd be pretty equal to a well setup carburator, especially at WOT. Part throttle economy will be better with TBI, though, as would drivability.

 

The killer on any straight six with a 4bbl, is going to be cylinder distribution. So far, I've not seen a way to mount one carb in the middle of six runners, and get around that issue. The closest an OEM has gotten was the Slant-6 Hyper-pak, which has LONG runners, trying to minimize the differences in length.

 

Even the SU carb manifold has distribution issues, on runners 2 and 5, in some applications.

The advantages of converting to efi though, are that you dont have to play 'by the rules' . The advantage now, as I see it, is the removal of the restrictions required to make a carb, by it's very nature, work. Top end power will increase IF there was some reduction to the intake flow potential caused by the carb. Maximum flow potential through the manifold can be realised.

 

I chose this route (4 bbl efi) because I had worked on carbs for way too long and even though I landed on what I believe to be a 'well setup carburetoer' for my application, I wanted to experience the difference EFI would make. The longer term option will be to run a blow thru turbocharger through the TB for that added little something!

 

The large variety of 4 barrel carb manifolds for the L series sixes are more than what was on offer for EFI and even though the stock efi manifold supports some excellent, well developed and powerful engines, I just don't like them. That's not a rational comment I know, but so is asking someone their favourite colour or who is the sexiest woman in the world or.... For me, the variations in the carb. manifolds design will alter the running/operational characteristics of the engine so much, you could 'tailor' or tune your engine in much the same way you do with head and cam specs. Yes, I concede that there will be some inherent design flaws using these manifolds BUT I think you're only going to find them as 'limiting factors' at much higher states of tune. For the street and even for some track work, they're fine. I testify to these statements based on my own experiences with these manifold/carb arrangements for the last 25 or so years.

 

I would love to design a manifold specifically for the throttle body and injector arrangement. You don't have to worry about things like fuel bowls so the whole TB could be turned 90 degrees so air entry could be side draught. Six tubes (equal length or otherwise) could snake and merge as do header pipes do, to a plenum under the TB. Just an idea. 

 

The twin su manifold  'seems' to be a reasonable piece of kit, how do you account for flow variations you're aware of? I would have thought the engineers at Nissan would have been fairly close to spot on, working on stock engines (stock cam timing re induction pulses/reversion etc)?

 

[Tony D]

It's popular in Japanese Tuner Magazines now to fit injectors to an existing Mikuni Setup, strip out the venturis, and tune the EFI to see what they get. In every case I've seen, it's been an advantage in peak and power under curve. It's basic physics, less pumping losses means more efficiency.

[Tony D]

I was so busy in Manly doing the failure investigations, I didn't even have time to properly hoon the Mercedes I hired!

 

Such a shame!

 

Hooning before phone calls!

 

Oy!

[Xnke]

Look at the runners between 1-2 and 5-6 on the SU manifolds...there isn't length before they merge into a single runner, so this is the theorized order of events:

 

1 draws full charge, being directly in line with the carb, 5 draws charge stealing a little from 6, 3 draws charge, 6 draws a full charge, being directly in line with the carb, 2 draws charge stealing from 1, 4 draws charge.

 

If you have the SU's OR the port fueling manifold conversion like Z-ya and I are running, tuned such that 1, 3, 4, 6 are all at stoich, 2 and 5 will be a little rich. Tune for 2 and 5 at stoich, and 1,3,4,6 will be a little lean. It happens on the port fueling manifolds due to the same charge robbing, the vapor floating near the port gets drawn BACK up the manifold, then back into the adjacent port. With a stockish cam, or a cam setup to minimize low-speed reversion, then this is not so much a problem, but even stock engines with SU's show this if you check the plug colours.

 

Longer runners reduce this tendency, by making the airflow have to reverse along a longer path, which is doesn't really want to do if it isn't easy.

 

I *think* that this is why this happens. I could be wrong, but I'm not the only person who has noticed this issue with the carb manifolds.

Edited January 11, 2013 by Xnke

[240zphilly]

Awesome that you followed through with this. Glad to see its working well for you!

[ozconnection]

Awesome that you followed through with this. Glad to see its working well for you!

 

Yep, all my friends are saying the same thing. I do like the auto tune feature in Tuner Studio. It's so cooool!

[Xnke]

I do have to agree, that is a sweet looking setup. I really like that fuel rail look.

 

I fully understand the "This is the way I'm going to do it, because it looks awesome and it's my car" thing, that's 85% of the reason I have the intake I have now, and the one on the bench. Same with Derek, and his Trumpets, they're just flat cool.

[240zphilly]

Oz, you gotta keep us up to date when you decide to pressurize that thing. I'm excited for you to see the results.

[ozconnection]

Ok, will do.

 

I will take this thing to the dyno once I'm happy with the tune. Then, after the other stuff is put on, I'll take it back to the same dyno to see what difference there is.

 

So much to look forward to in 2013!

[240zphilly]

What EMS are you running that does the self tuning? How do you like it? Was it costly?

[ozconnection]

Megasquirt 2 version 3 motherboad. Tunerstudio software has an auto tune feature. It's sick az! I've had some issues getting the innovate WB proper and stable voltage. Now I think I have that sorted, it's tune time.

[240zphilly]

Sounds great... celebratory burnout video? What does the butt-dyno tell you? Making good power I hope. 

[ozconnection]

I drove it around the block the other day. Response is good and power is adequate    I still have to learn how to tune with Megasquirt.

 

It's only a matter of time.

[Xnke]

Using the Autotune feature is pretty easy; but you need to make sure your injector dead time is spot on, you have your voltage adjustments correct, and that you have your AFR tables exactly the way you want them. The delay stuff is not terribly important for the first few passes of autotune, but as you get more data on paper you do need to check them to see if they need revising.

 

Also, once you have the above settings locked in at the best you can get, the autotune feature is AWESOME for tuning spark map. Tell it not to update the controller, and adjust your timing in the area of interest...then let the autotune run and show you what kind of difference it made to AFR...it also shows up in the Delay settings, and MAPdot traces. You can simulate a LOT of fancy equipment with the datalogging, but the Autotune stuff shows it in such a visual manner that it really clicked for me.

[ozconnection]

I've done a lot of reading from the sites and I still see some big grey areas. The trouble is you dont know whats important and what isn't. You could read a sentence that could make a HUGE difference to the tune overall, but skip it because its included with other stuff that looks fairly irrelevant.

 

Injector dead time for instance....wtf is that??

 

Maybe I should have bolted all this stuff onto an old cluncker. I really don't want to wreck my lovely new engine whilst hit/miss with this new efi stuff. I had a map sample error and found buggar all information as to what it was or how to fix it. Now, it seems to have gone. My o2 reading on tunerstudio is still reading stupid reading, one second its 9 to one, then 22 to 1, and its sending autotune into circles....the engine runs like crap as you can imagine.

 

I will plug the innovate into the laptop, maybe there is a silly setting there thats causing this to happen.

 

OR, I'll buy another LC1 and try that. Error code 9 is gone now with my mods but the thing is still silly as mentioned above. The o2 sensor is brand new and properly calibrated.

Edited January 16, 2013 by ozconnection

[skirkland1980]

I had many problems with my Lc1. I got 2 bad units. Finally swapped for an Autometer. A few years later still no problems with the Autometer.

[ozconnection]

I did notice that the little red LED sometimes does strange things too, not the usual style of blinking that I see normally with warm up or error notification.

 

I might buy another LC-1 and oxy sensor, and try that first. The LC-1 was a second hand unit I bought with the Megasquirt EFI setup I have and I think that the new o2 sensor in the exhaust isn't genuine. The cable is different slightly in its construction but the part number on the plastic bag was correct. (as if thats convincing)

 

We'll see what happens.

 

PS I've gone off topic with this thread. Sorry mate, I apologise for that.

[SuperDan]

Oz, what you are doing looks similar to what I have been mocking up.