Let's talk intake design

Still noodling over all the parts for the yugo build and really trying to square away component choice for the head so its time to talk about intakes.

I have 2 FI intakes, one Yugo, one Fiat. I'd like to use the Yugo purely for aesthetic reasons to keep the "sleeper" vibe, but let's look at what we have and make choices based on good performance instead.

Both intakes side by side:

Of note the Fiat uses high impedance injectors, the Yugo uses low impedance (or vice versa I could be confused) Whichever one the Yugo has are what I need for the planned microsquirt setup.

So the Yugo is a long runner one piece design

The Fiat is shorter runners and a 2 piece

Yugo ports are about 27.5mm red line denotes where a stock non-efi gasket sits to determine if I could modify those gaskets since Yugo EFI bits are harder to find.

Fiat ports are about 28mm and finished much better

With the cam and work to the head the motor will be high revving and a bit weak on the low end. I seem to recall that longer runners are better for low end so maybe the Yugo intake will be a nice compromise on that end. I could just be making a bunch of stuff up though.

Share with me your thoughts, knowledge and experience.

Don't forget, smaller runners will boost your low end but the high end will suffer.

I don't know how much difference 0.5mm will make though.

If it were me, I'd use the Fiat manifold because of the two piece design. You could split it at the joint and play with the runner length by adding and subtracting spacers to get the powerband right where you want it.

Of course, that's just adding one more thing to go wrong as well.

Shawn

yeah, the 2 piece design seems to open up a few options. Not too concerned with the runner diameter as those were rough measurements and they can always be modified.

Yeah, killing the high end is bad, this engine will have its happy place in the 6000-8000 rpm range.

Thinking of using the lower part of the Fiat manifold and building something else off of it. Might be a good start to an ITB setup ;)

I was about to make the ITB suggestion. For top end you want short, fat runners. As I understand it (which is not to say scientifically), the ideal runner will offer high volume flow with the velocity of the charge peaking near the torque peak. I'd be looking at motorcycle engines that peak around 6-8k RPM for ideas.

Ok so give me the idiots guide to ITBs so I can mull that idea some more. I know squat about them other than there seem to be sets of motorcycle take offs on the bay of e's for around $100

When I was milling over this same question, I liked the Fiat intake better for basic design and flow, and it enabled bringing the intake piping very direct and straight (I was also planning for a future turbo, so the inlet straight over the front gave much more space to direct the lines).

However, the injector question was a big one. I settled on the same issue you did- I felt I had to stick with the Yugo injectors to make the MS work (not totally true). You're not gonna get the Yugo injectors to fit in the Fiat intake.

One other option is to attempt to add resistors, and use the high impedance injectors. Somewhere in all that stuff I gave you, there should be a small aluminum bracket with the resistors already mounted. It will fit neatly bolted to the intake, IIRC. That's what Matt and I were working on.

I think both designs are fairly lacking and at this point if I'm going all out on the head work then it probably makes sense to start looking into ITBs. I also think I may keep the stock 1300 that is in there fairly stock and just throw the SX1 cam at it. Should make a good autocross motor, lots of low end but still able to rev fairly well.

I have to further modify the PBS head to make either of those intakes work right now so more and more I'm thinking to stop looking at "off the shelf" solutions.

JThw8 wrote: Ok so give me the idiots guide to ITBs so I can mull that idea some more. I know squat about them other than there seem to be sets of motorcycle take offs on the bay of e's for around $100

Everybody I know personally (myself included) that adapted sport bike ITB's to their cars removed them within a year. 10-12 people with cars ranging from street cars to dedicated autocross cars.

They sounded amazing but with MS1 on a 2.2 board and the available firmware/megatune at the time it was a nightmare to tune properly. Throttle tip in was dreadful. I did it on a VW 16V and peak power was unchanged when I went back to a stock manifold and throttle body.

MS2 handles ITBs much better by introducing an ITB mode that adds MAP- based tuning at low rpm/throttle openings and then using Alpha-N for higher RPM/throttle opening.

With that said, I'm using MS1 2.2 with the extra code and ITBs and its working ok. I will be going to MS2 since I'd like to get the tuning a bit closer.

I'm also running high impedance injectors without a resistor pack. There's two solutions for this on the market:

The fly back board:

http://www.diyautotune.com/catalog/megasquirt-flyback-board-kit-for-pcbv22-ecus-p-44.html

The Peak & Hold board from JBPerf:

http://www.jbperf.com/p&h_board/index.html

The JBPerf board allows you to run the hi-res code which helps with more finite tuning.

As for ITBs and tuning with MegaSquirt, this might help:

http://www.77e21.info/megasquirt.htm

Good luck!

Depending on your peak rpm... shorter will help develop the low end....

I modified my 89 model with a 90 manifold from a Celica, and my peak torque is now @ 2700 rpm.... AND she still pulls well past redline

I did a bit more then just swap manifolds.... - http://www.hachiroku.net/forums/showthread.php?t=24099

I use the Yugo intake because it gives you more fuel injector chooses. Also added safety as I did not wont to take the chance of having 8 more places for the fuel to leak on the exhaust.

I vote motorcycle carbs. Find a bike that makes similar power per displacement/ per cyl, make some adapters (if youre patient you could widdle some out of aluminum or steel with a die grinder and a drill), done. Flatslides are very low restriction as no butterfly remains in the flow path, they are lightweight, cheap to acquire, aesthetically pleasing, and easy to work on. Jets are available locally, as are replacement parts.

With a big fat screamer cam you will make more power with the shorter intake. Though as mentioned, you inadvertently up the odds of fireball with all those hoses and clamps on a non cross flow head.

WRT aesthetics, how many people on this planet remember clearly what a EFI Yugo looks like under the hood?