What happened to your Discovery 2 today?

Re broken studs OUCH!

It has got pretty hot EGTs then.

When I replaced my manifold I elongated the end holes so that the manifold could slide as it lengthened due to heat and added Belleville washers to aid the sliding.

I got the idea from the Toyota manifolds which are in two pieces with a sliding joint halfway along.. My assessment is the studs break from side forces from the manifold elongating as it heats up.

I note that the second port seems to have peeled away some aluminium , or maybe another broken stud. I also slotted the second port bolt holes to a lesser extent than the end ones. If aluminium , you should chase the threads.

My solution was
remove webs, flatten face, ceramic coat in and out, slot the end holes and intermediate holes, Belleville washers, Mercedes Benz studs bought from UK.( which are supposed to be better material)
Try not to exceed 700C for any length of time.
So far so good for about 30KK
Regards PhilipA

Why not go allisport manifold ceramic painted? I run that

Quote:

---

Originally Posted by PhilipA

Re broken studs OUCH!

It has got pretty hot EGTs then.

When I replaced my manifold I elongated the end holes so that the manifold could slide as it lengthened due to heat and added Belleville washers to aid the sliding.

I got the idea from the Toyota manifolds which are in two pieces with a sliding joint halfway along.. My assessment is the studs break from side forces from the manifold elongating as it heats up.

I note that the second port seems to have peeled away some aluminium , or maybe another broken stud. I also slotted the second port bolt holes to a lesser extent than the end ones. If aluminium , you should chase the threads.

My solution was
remove webs, flatten face, ceramic coat in and out, slot the end holes and intermediate holes, Belleville washers, Mercedes Benz studs bought from UK.( which are supposed to be better material)
Try not to exceed 700C for any length of time.
So far so good for about 30KK
Regards PhilipA

---

Quote:

---

Why not go allisport manifold ceramic painted? I run that

---

Cost, benefit!

IMHO , and thinking about it, over the years I have come to the conclusion that free flow manifold's only benefit may be faster spool up, and maybe more boost at low boost levels for a given fuel input.

The wastegate controls maximum boost levels and any turbo on a TD5 can reach the wastegate cutoff. Once you reach wastegate cutoff "that is all she wrote."

When my modulator hose got a hole I saw 28PSI sometimes before the ECU cutout actioned but a VGT could go much higher.

I think there could be some benefit in gas flowing the head and inlet manifold but ultimately it is the boost limit that determines power for a given input of fuel. To me that is why Toyotas have very ordinary and cheap exhaust manifolds on the V8s.

Of course if the fuelling is increased then more power, as evidenced by the steam engine like USA hot diesels, but highly anti social.

Of course the big limitation is EGTs and there is only so much power you can extract from a 2.5litre with one squirt before the EGTs become excessive, as found by the poster who appears to have a VGT.
Regards PhilipA

Quote:

---

Originally Posted by onebob

Okay.... I'll be the first to ask
Do you intend it to be a "permanent" modification?

---

I will run it thru summer and track it with the nano.

It's a curiosity thing, and answers a question by doing not speculating.

I like to do things and then I learn.

If the fuel temp creeps up on a 200k test drive I will put in an ebay finned air unit, anything to avoid the rats nest of coolant hoses and joins.

Also they build these things to get landed off a ship and operate anywhere in the world of extreme temps and weather conditions, Adelaide is mild climate

The nano log is there for anyone to check that wants to.

There doesn't seem to be much rhyme or reason as to when the manifold will warp/ pull the studs etc.

Obviously more heat will speed it up though, I think possibly the main reason they let go is the webbing and small Bolt holes which stop the manifold moving how it needs to when expanding and contracting at different rates to the head.

I've personally not had one let go after it's been modified and I'm running about 2 bar or so, but not very high EGT it has to be said.

Cheers
James

Quote:

---

Originally Posted by AK83

Is this supposed to be some kind of mod to increase power or efficiency or something?

---

Nope just less coolant hoses to leak and more space to get hands in, and I hate under bonnet clutter.

Something will go in its place If I see it really is needed, just not hanging off the inlet manifold.

Have tools, curiosity, have half a brain, will experiment.

Quote:

---

Originally Posted by johnp38

Nope just less coolant hoses to leak and more space to get hands in, and I hate under bonnet clutter.

Something will go in its place If I see it really is needed, just not hanging off the inlet manifold.

Have tools, curiosity, have half a brain, will experiment.

---

The late model fuel coolers are somewhat more discreet, but wouldn't be a straight swap from memory.

Quote:

---

Originally Posted by PhilipA

Cost, benefit!

IMHO , and thinking about it, over the years I have come to the conclusion that free flow manifold's only benefit may be faster spool up, and maybe more boost at low boost levels for a given fuel input.

The wastegate controls maximum boost levels and any turbo on a TD5 can reach the wastegate cutoff. Once you reach wastegate cutoff "that is all she wrote."

When my modulator hose got a hole I saw 28PSI sometimes before the ECU cutout actioned but a VGT could go much higher.

I think there could be some benefit in gas flowing the head and inlet manifold but ultimately it is the boost limit that determines power for a given input of fuel. To me that is why Toyotas have very ordinary and cheap exhaust manifolds on the V8s.

Of course if the fuelling is increased then more power, as evidenced by the steam engine like USA hot diesels, but highly anti social.

Of course the big limitation is EGTs and there is only so much power you can extract from a 2.5litre with one squirt before the EGTs become excessive, as found by the poster who appears to have a VGT.
Regards PhilipA

---

My replaced manifold will now be tapped for EGT at the collector so I can see how bad my tune is :P with the de-webbed mods. Any one have recommendations for replacement studs the ones that came with that crap ASI manifold are a little bit shorter than the factory ones which wont be ideal I suspect.

Quote:

---

Originally Posted by johnp38

I will run it thru summer and track it with the nano.

It's a curiosity thing, and answers a question by doing not speculating.

I like to do things and then I learn.

If the fuel temp creeps up on a 200k test drive I will put in an ebay finned air unit, anything to avoid the rats nest of coolant hoses and joins.

Also they build these things to get landed off a ship and operate anywhere in the world of extreme temps and weather conditions, Adelaide is mild climate

The nano log is there for anyone to check that wants to.

---

Curiosity... I totally get that, but my primary concern is how you modified the fuel line.

I'm not sure about this but from what I know about different metals and expansion rates, everyone is saying the manifold expands and breaks the studs, I believe it is actually the head expanding more than the manifold (this would be easy to see, if the rub marks are on the outer edges of the manifold then it is the head pushing the studs into the manifold. But what ever happens I know they break (I've got at least one to do) the heat definitely causes warping but again I think this is due to lack of movement in the design of the manifold, I will be de-webbing mine in a week or so and see what happens after that.

anyway just my 2 bobs worth

cheers

John