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Pav

Manifold cracks, can they cause loss of boost

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Hey guys, after some advice and opinions on this.

If, for the sake of argument my manifold was cracked and blowing, could/would it cause a substantial adverse affect on my boost level?

My boost comes in and peaks as usual but instead of settling out, it keeps dropping (for instance it would come in and peak at 1.1 bar but drop to 0.9 bar past 5krpms)

I have a feeling your answers will be yes, but I wouldnt mind some opinions of people who have experienced this problem before.

Cheers,

Pav

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i would have thought there would be a noticeable loss of power throughout the rev range or not reach peak boost level.

or if it's not a huge crack like you said it might only effect the highest rate of flow which would be in the higher revs.

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Hmm, thats what Im thinking, It might explain my last two RR graphs, high torque upon intial boost, but power dropping off as the revs rise.

Hence instead of 200bhp and 190 ft/lbs for arguments sake, im getting 180bhp and 195 ft/lbs.

Annoying problem if it is the manifold, but solvable none the less!

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Power will normally drop off as the revs rise.

As for having less power than torque. NOthing to worry about.

But to answer you initial Q, if the mani was cracked, you would lose out all across the rev range, not just peak power.

From what im reading, your car seem to be just fine, just the little turbo that cant keep up the pressure.

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Yes a crack would make a massive difference. I have recently realised ther has been a loss of power in mine and i have found some good sized cracks in the manifold. The first sign is a louder exhaust note. Thats is when i noticed mine had a problem.

Bourkey

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Power will normally drop off as the revs rise.

As for having less power than torque. NOthing to worry about.

But to answer you initial Q, if the mani was cracked, you would lose out all across the rev range, not just peak power.

From what im reading, your car seem to be just fine, just the little turbo that cant keep up the pressure.

lol, it may still be a little ct9, but it has at least been hybridised to keep it from dropping off in the higher revs. When I first started using it I dont ever remember it dropping off at all. It only seems a recent development, but I am open to the possibility that even a hybrid cant hold full boost to redline.

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Yes a crack would make a massive difference. I have recently realised ther has been a loss of power in mine and i have found some good sized cracks in the manifold. The first sign is a louder exhaust note. Thats is when i noticed mine had a problem.

Bourkey

Yeh, mine sounds louder, and very tractor-ish when you get the bonnet open and have a listen under throttle blips.

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sounds like the mani is cracked.i should no mine split 8 times and you could tell when it had gone.and as you said theres a tractor type noise inthe bay area.have you felt around the mani to see if you can feel the gases leaking.Dont you have a mild steel one if i remember?

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Might be a hole in your exhaust making the noise of you've got a mild mani, or you have a couple of loose mani nuts.

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^^^LOL :)

Well Im sure its a one off as Danes manifolds have not had any problems in the past, but mine almost definately has a crack, quite a big one by the look of it located in the centre of the collector. Upon blipping the throttle, I can feel the gases escaping quite prominently, so I can imagine the potential escapage on full boost.

I have checked that the bolts are tight, all the mani gaskets, studs and nuts were toyota brand new parts too.

Im sure Dane will sort it out, though hes a top bloke. :)

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Guest Enzo
^^^LOL :)

Well Im sure its a one off as Danes manifolds have not had any problems in the past,

Im sure Dane will sort it out, though hes a top bloke. :)

there are a few cases of Danes manis cracking now, must be something with that batch maybe?

eather way he will sort it for you, but i can imagine it being an inconvienience for him if more crack.

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are they SS or mild?

ss ones dont usually respond well to re-welding. but mildsteel ones are pretty secure once rewelded.

id also wrap it up before it goes back on of it isnt already.

manifold wrap can help stop then cracking. in this weather they cool down alot faster when off throttle and that is the main cause of cracking.

wrapping them up helps then cool down at an appropriate rate and can help with cracking problems.

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there are a few cases of Danes manis cracking now, must be something with that batch maybe?

eather way he will sort it for you, but i can imagine it being an inconvienience for him if more crack.

I heard of only one other issue with one of his, and it turned out to be something else as opposed to a crack, the customer was just overreacting at the time iirc. These things happen at the end of the day, you cant make a large quantity of high stress products and not have an issue with one of them every now and then. Dane has shown his true colours in the way he dealt with the other chap (which was very well), and I trust him totally.

His new range of manifolds that are guaranteed now and look much better again. I just wish he had those out back then as I would almost definately have bought one of them instead. :) At the moment im totally skint so thats out of the question. :)

are they SS or mild?

ss ones dont usually respond well to re-welding. but mildsteel ones are pretty secure once rewelded.

id also wrap it up before it goes back on of it isnt already.

manifold wrap can help stop then cracking. in this weather they cool down alot faster when off throttle and that is the main cause of cracking.

wrapping them up helps then cool down at an appropriate rate and can help with cracking problems.

Its a mild steel one mate. Its also wrapped with mocal heatwrap on the runners, but the point at which the crack appears to be is where wrap cant easily be placed, right at the rear/center of the gases "coupler" (where the runners all meet).

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I would get it off and sorted asap mate before it turns undrivable. The day i went to sort mine out i had to move the car a couple of yards and i started it up and it didn't sound healthy at all. Luckily i was taking it all off that day. Sort out the small problem before it becomes a big one :).

Bourkey

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i got the new mild steal sps mani nd the face isnt quite flat and it's causing a small boost leak so will be getting it skimmed soon.

Dane is a top bloke 100% and will deal with whatever problems arise with his products...he is helping me out at the moment :)

Pav just get the mani off and get it temp welded till you no what you wanna do...whether it be upgrade to Danes new ram mani or another mani or perhaps get a more permanent weld put in place.

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