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Boost pressures?


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Getting ready to purchase gauges.What is the typical factory boost pressure range? Trying to decide on a 10 - 30 psi guage or 10 - 50 psi.Also, I'm going to install an EGT guage as well. Were do most guys put the thermocouple probe? I'll probably drill a hole & tap 1/8 npt on the top of the exh manifold pre-turbo - that is right there before the flange where the manifold bolts up to the turbo. That's where I did it with great success in my isuzu NPR diesel.And for you guys who are going to warn me about metal drill/tap chips falling in and wrecking the turbo, don't worry as the best way is to drill and tap slowly while engine is idling. Thats right! Get up there and drill while engine is running. Preferably do it on first start up of the day as it only takes a couple minutes and you don't want to work on a hot engine. As you poke through, the pressures from the exh gasses blow the chips up and out. Just be sure to wear safety glasses!Soon to be installed mods: fuel bossPotential future mods: 50hp injectors & edge comp.Thanks!

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Since you are not going to a big turbo you can use the 0-50 psi gauge. If you used the 30 psi gauge you can over pressure it and then it is no longer calibrated and not reliable. Far as the pyrometer, in the manifold is the best place (pre-turbo). Just remember there is a divider right in the center of the manifold. Drill the hole at about 1/2 way between the rear of the manifold and the center of it.

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Since you are not going to a big turbo you can use the 0-50 psi gauge. If you used the 30 psi gauge you can over pressure it and then it is no longer calibrated and not reliable. Far as the pyrometer, in the manifold is the best place (pre-turbo). Just remember there is a divider right in the center of the manifold. Drill the hole at about 1/2 way between the rear of the manifold and the center of it.

Thanks for the tip on the divider. 1/2 way between the rear of the manifold and center of it? Not sure where you are describing. Can you give me a reference point? When you say "rear" exactly where is that? Thanks!
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I was initially thinking ISSPRO, but I've just decided to go with Mcnally Guages. I've been running one of thier boost / egt combo guages in my isuzu box truck since 2009. Great guage, nice look. Black face, white letters, led blue illumination at nite. it has a dial for the boost and digital egt. Anyway, Thanks for the tip on the boost pressures. I just talked to the engineer at McNally they make a 0 - 50 boost / egt combo. I'm not an engineer but he assured me the 0-50 is accurate across the full range of the dial. And they do custom gauges as well so I'm going to have them make a custom dial for a fuel pressure / trans temp guage. This way I can get four data points from 2 physical gauges & mount on the a pillar. Unless I can find a 2 pod dash mount that is! Here is the link for mcnally if anyone is interested. http://www.mcnallyelectronics.com/index.htm Great customer service by the way. Good prices too. I think they started off as an aviation guage manufacturer and spun off onto auto stuff because one of their engineers has a vw TDI.

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Thanks for the tip on the divider. 1/2 way between the rear of the manifold and center of it? Not sure where you are describing. Can you give me a reference point? When you say "rear" exactly where is that? Thanks!

When you take the turbo off you will see what Tom is talking about. It is divided into a front and rear at the outlet of the manifold.
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When you take the turbo off you will see what Tom is talking about. It is divided into a front and rear at the outlet of the manifold.

Thanks, Dave! I guess I wasn't too clear on the divider. It divides the outlet so that 1, 2, &3 are separate from 4, 5, &6. #6 cylinder is usually the warmest cylinder. That is the reason to measure the rear half. This may help: https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcSKDRzjZOzZYM9max1lz9-9NP8IA8k2N9e3-lwlwFlIF6gZR_-How
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Thanks, Dave! I guess I wasn't too clear on the divider. It divides the outlet so that 1, 2, &3 are separate from 4, 5, &6. #6 cylinder is usually the warmest cylinder. That is the reason to measure the rear half. This may help: https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcSKDRzjZOzZYM9max1lz9-9NP8IA8k2N9e3-lwlwFlIF6gZR_-How

A picture is worth a thousand words as they say!!
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Thanks, Dave! I guess I wasn't too clear on the divider. It divides the outlet so that 1, 2, &3 are separate from 4, 5, &6. #6 cylinder is usually the warmest cylinder. That is the reason to measure the rear half. This may help: https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcSKDRzjZOzZYM9max1lz9-9NP8IA8k2N9e3-lwlwFlIF6gZR_-How

Thanks for the info. The picture clarifies it big time.
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