unheated inlet manifold - practical option?

[GreenV8S]

Anyone got experience (good or bad) of running an an injection setup with an unheated inlet manifold? This would be for normal use all year round. I expect it could be a problem with carbs, but would an injection setup be OK?

[HarryW]

Not sure it would make that much diference myself. I take it the heating is constant (water jacket) on the RV8, which is bad for a cool air flow into the engine, as opposed to more modern systems where the heating is electrical and hence switchable .
I thought the bigger engines ie 500's didn't have the water heating connected anyway Peter , could be totally wrong as usual though.

Harry

[GreenV8S]

The injection manifold has a hot water chamber built into the base on all models. The throttle body also has a small separate hot water chamber which is fed by external hoses - this is left disconnected on some models. As I understand it, the heating is there to ensure the fuel evaporates to give a uniform mixture even in very cold weather. Which makes sense if you're running carbs, but does it matter for an injection setup? Enquiring minds need to know!

[shpub]

Pete

The 520 has been running unheated in both the ACT and triple throttle incarnations. No probs so far. The air box has certainly done wonders for cold air feed though.

Steve

[GreenV8S]

Was that using an injection manifold Steve?

[deltaf]

If your using a carb on an injection manifold, you could find problems with fuel puddling and drop out.
Injection manifolds are designed to run dry, and shouldnt need to be heated, as theres only air going thru them.
The heated carb manifolds are used to ensure re-vaporisation of the fuel that does drop out.

[GreenV8S]

Makes sense to me that a carb manifold has to be heated, but I don't understand why the standard injection manifolds are also heated. Any ideas?

[deltaf]

Nope, makes no sense to me at all!
Id say block off the water inlet(it is water heated???) at least youll get some small power gains maybe due to a denser charge.
Had a water heated intake on the audi, i blanked it off, and never had a problem with it, and that was with a carb.

[350matt]

It's all the do with emissions as the manufacturers would rather suffer a bit of a power loss than fail the cold conditions emission test. But otherwise you should be OK with injection car in std english weather.

Matt

[shpub]

GreenV8S said: Was that using an injection manifold Steve?

Yes. In both cases.

[donaldhunter]

In theory an unheated inlet manifold should be just fine with injectors. But on a Rover V8 it would require a custom inlet manifold. The thermostat is mounted in the front of the manifold and water flow into the heads is through the manifold.

[v8 racing]

What manifold is this were talking about? the rover/tvr v8? if so the inlet manifold is not heated the water jacket at the front is purely a link at the very front from one head to the other hope this helps.

[wedg1e]

Just had the inlet manifold off my V8 and there is indeed a link at the front between the heads: this then feeds the thermostat housing and also a pipe tapped off underneath that nips off to the heater... so there must be an element of manifold heating although initially it may be unevenly distributed until the engine warms... probably irrelevant as none of us would be nailing a cold engine, now would we?!
I suppose you could bypass the heater feed (and in fact my mate's 400SE has a different plumbing setup in this respect, with the heater pipes running along the side of the plenum instead of underneath it: maybe his car has a later manifold with different flow arrangements?) but I think you'd struggle to separate the head-to-thermostat section from the rest of the manifold - probably not a machining impossibility though I haven't considered how you might then mount the 'split' manifold assembly back to the heads.
I've just fitted a composite inlet gasket instead of the plain tin thing: maybe that in itself provides a degree (no pun intended) of thermal isolation?

Ian

[SLiller]

Iam currently fitting Injection to a Rover V8 in my TR.
Ive come across this very problem with the heater hoses, I need two for the heater matrix and the manifold I has only has one input pipe and the themosat output. There is a blanking plug behind the input pipe that can be unscrewed and I guess a water pipe fitted. Then bolt another heater pipe next to it from an old carb manifold. I think?!. There are two pipe bolted onto the top injector rail, looks like an after thought!.
I think there needs to be a small pipe from below the thermostat housing to the back of the water pump to act as a bypass untill the thermosat opens and allows flow into the rad.

Sound reasoning?.

[GreenV8S]

The manifold has a joining chamber that forms the back of the stat housing. The chamber has one outlet at the front, and one at the back. The one at the front is the bypass and should be connected directly to the water pump inlet. The one at the back normally feeds the heater, and the pipe bringing the return from the heater is normally routed back under the manifold so that the bypass and heater return hoses both appear out the front of the manifold under the stat housing. You should have an SD1/EFI water pump which has two inlets to take these two hoses.

The bypass pipe is absolutely essential and must go straight from the manifold to the water pump inlet. Heater feed and return are optional and can come from anywhere you fancy, and don't have to be routed under the manifold (I've seen cars with these two pipes running on top of one of the rocker covers.)

The other pipes you may seen in the area are a pair of small bore pipes from bosses on the front/top of the manifold to the throttle body, these supply the dreaded throttle body heater. Worth disconnecting and blanking these off unless you live in Siberia.

[ssc1]

well at least that has answered why i have these two small bore pipes disconnected and blanked as they went to the throttle body , would it not be better if they were connected to each other or one removed and the other connected to the stub on the inlet manifold just to help flow or would this not be a good idea , i think it would tidy things up a little rather than have two hoses lying loose under the plenium.

[GreenV8S]

ssc1 said:

would it not be better if they were connected to each other or one removed and the other connected to the stub on the inlet manifold

Doesn't make enough difference to the engine to worry about, but they are connected together on mine and I agree it does look tidier.

[wedg1e]

Mine was plumbed such that the inlet manifold stub fed the throttle heater, then the outlet from the throttle heater went to the header tank.
So it was simple matter to re-route the inlet manifold stub direct to the header. In fact I took the heater body off altogether: now I can get my hand under the throttle body to fish stray tools out!

Ian