Thoughts on this Manifold design?

[Frank Clark]

At some point, I am looking to ditch the factory manifold. This is on a built 1UZ VVTi with a large turbo in a light car (2600-2700lbs).

I really am not concerned about low RPM performance. I would like the new manifold to be lighter and suffer less from heat soak. My new manifold needs to have the throttle body in the same place as my current modified factory manifold, because the inter-cooler basically feeds directly into the throttle body, with only a short piece of silicone tubing in between.

Current setup:



My current thought on a new manifold:




Obviously the rendering only shows one fuel rail/injector holder set and part of the body is left off, but you get the idea.

I am thinking, cast the trumpets as two identical sets. Cast the injector holders. I have a bit to properly cut the injector holders/fuel rail to seat the injectors. Weld the body up from sheet and pipe. Machine the TB mount from billet and weld it on. Use bulkhead fittings to get the fuel in. Use hermetic fittings on the back side to "plug in" the injectors. Use clear plastic for the top, but it will probably actually need to be an aluminum frame with smaller 'windows' as the pressure on that large a piece would be excessive. I definitely want to be able to easily pull the top off to maintenance injectors and wiring.

I have the 3D printer working on a trial set of trumpets - it's going to take days to print...

Comments/Suggestions?

 

[Zuffen]

If heat soak is a problem you can make phenolic spacers to go between two intake gaskets. I did this on a blown engine and it did cool things down a little.

Have you thought about milling the trumpets from the same stuff. Would hold the heat down and it's easy to machine but is carciagenic.

I agree the plexiglass roof may blow but if you make it thick enough it should hold up but the injectors would probably create weak spots where stress crack could/would propagate.

I do like the positioning of the injectors. This would make for outstanding mix of fuel/air.

 

[Frank Clark]

We also race sprint cars. While we don’t have them, down nozzle injectors are not uncommon.

I figured it will 1) give a straight shot towards the valve, 2) won’t hamper air flow, 3) will give a longer path for the fuel so to take advantage of evap cooling from the ethanol (running E85).

 

[Frank Clark]

Did you have someone water jet cut the spacer?

 

[Zuffen]

No I purchased a fuse board panel (the panel circuit breakers are mounted on in Australia, and for all I know elsewhere) and machined my own at home.

Used a dust mask and a drill press and rotary burr. Turned out well and sealed up well.

 

[gloverman]

Now i think i have seen a similar design on another engine (which always makes me a bit excited as its a gorgeous thing) however the injectors were seated on the outside of the top plastic cover and pointed directly into the trumpets. Saves trying to get all the wires and fuel into the inside of the manifold. I think it has 5000cc moran injectors which hopefully have quite a straight flow pattern. Ive been trying to find a photo but no luck so far.

 

[Frank Clark]

I have a design like that modeled but I don’t like the one I did.

I “feel” like the tips of the injectors need to be below the top of the trumpets to insure all of the fuel intended for a cylinder makes it to that cylinder. Really don’t know if that’s necessary, but it seems with all the turbulence it could be a problem if they are too high. Keep in mind that with valve overlap at low RPM there can be reversion, though with VVTi this should be all but eliminated.

So in my external injector version I sunk the injectors as far into the lid as possible but the the lid was still within an inch (25mm) if the trumpets.

 

[Frank Clark]

Zuffen, are you talking about household circuit breakers?

 

[Zuffen]

Yep!

In Australia we use the phenolic board to support older switchboards.

modern Circuit breakers are in purpose designed boxes but back in the day old ceramic fuses were mounted on phenolic and (sometimes) asbestos board.

Still readily available here.

I have a small supply in the shed for when I need to insulate things electrically or thermally.

On the injector front do a Google search as there were plenty of F1 engines with that set up and they were above the trumpet.

 

[Frank Clark]

On the fuses, back in the day we had a different setup (screw in fuses). None of that old stuff is very common any more thankfully.

On the F1 engine injectors - Thanks! Like you said, there are lots of good examples from Ferrari to Honda, NA and Turbo - I had not seen those. I'm going to re-think that setup now.

And that led me to: https://www.efihardware.com/products/2581/Billet-External-Injector-Mount-Short

While I don't need those their notes about needing sequential injection all make sense (and yes I have sequential injection).

I also expect that when timed correctly, the burst of fuel is going to help get the air moving towards the valve.

 

[Frank Clark]

With Zuffen's suggesting (looking at previous F1 designs) and my realization that my plenum volume was off the charts, I reworked it to this. Shown without font/rear block off's for clarity. My trumpets don't fit this new design well, I will clean them up if this is what I go with.

The 'plenum' size for each side is about 4L without factoring in the runners. So about 200% which is on the large size. I understand this may impact throttle response slightly (probably more on decel rather than accel while on boost). But that is not an issue for this motor's intended use.

The slots feeding from the central area to the side plenums are intended to more evenly fill the cylinders - otherwise cylinders at the opposite end of the throttle body tend to get more air.

This design does get my injectors/wiring/fuel rails outside the manifold. And the injector bungs are simpler, I am sure I can just cut them on the lathe rather than having to cast them.

 

[Frank Clark]

One more to give a better idea what it would actually look like...

 

[Zuffen]

There have been a few good looking manifolds built for cars on this Site over the years.

May be worth searching old threads.

It does look good but may be a bugger to build.

Have you thought about building out of composites. It looks like that would be easier than casting.

 

[melvinmelvin]

One more to give a better idea what it would actually look like...
View attachment 13769

wow,
I like that one,

 

[cribbj]

Have you thought about building out of composites. It looks like that would be easier than casting.

Composites would help with the heat insulation too.....

 

[Frank Clark]

Composites (short of minor fiberglass work), is outside of my wheel house.

I don't think it will be too bad to build out of aluminum. I would 3D print the runners (one set for each side) and investment cast those. The injector holders are simple on the Lathe, and I have already made the bit to cut the inside for my injectors. TB mount is simple to cut out of billet. Rest would be aluminum tubing and flats. Some bending on the tubing used for the center section. I would weld it all up. Have had no issues welding my castings to extrusions or billet.

This is for a race car, so it's function over appearance. Needs to work well, hold up well and be straight forward to maintenance.

 

[cribbj]

I've often thought about coating the intake side (fuel rails, manifold, etc.) with a heat insulating ceramic/polymer coating and/or then wrapping it with the usual fiberglass stuff. Just to keep heat soak to a minimum. Probably more applicable for a street car than a racecar.

 

[Frank Clark]

I have ducted the roof scoop through the cabin to the firewall just above the engine. So the top of the engine does get plenty of cooling air at speed. But we are also talking about lots of heat as this thing is expected to run 5,000-8,000 rpm on boost for two 59 mile long legs. I've already grenaded two LS engines doing this...

But, One of the ceramic coatings would be simple to do (drop it off, they call me when it's done). There is also the reflective gold foils. They would work well on the sheet metal sections. Probably would not work on the cast portions.