The IDI Myth Thread....
Mountain Pass
Joined: Feb 2012
Posts: 244
Likes: 0
It may be disagreed upon here but I haven't had any issues yet with running exhaust out to a 6 inch single stack. I've been seeing that a lot of people over various forums would never think about opening up past a 4inch exhaust, but like I said I'm doing just fine going up to six (most if the exhaust is comprised of the 4inch; its the cheapo flex pipe mess).
I went this route because the boys who owned the truck before me ran 5 inch dual stacks, so the bed was already cut into. They even used a 4inch tip as an adaptor!!!
. My buddy had a spare 6inch stack he never used, so I just put it up on my truck and made it work.
Exhaust velocity is just fine, and the truck sounds great. I love driving it from a stop because it literally sounds like a boat
I went this route because the boys who owned the truck before me ran 5 inch dual stacks, so the bed was already cut into. They even used a 4inch tip as an adaptor!!!
. My buddy had a spare 6inch stack he never used, so I just put it up on my truck and made it work. Exhaust velocity is just fine, and the truck sounds great. I love driving it from a stop because it literally sounds like a boat
i ain't rite
Joined: Mar 2005
Posts: 65,601
Likes: 5,628
From: Marlboro Mental Hospital.
there is a big difference between a 3 inch downpipe, 3 or 4 inch pipes back to a 6 inch stack and a 5 or 6 inch downpipe and exhaust.
for 22 years my 88 had a 3 inch down pipe, to a 3 inch splitter to dual 4 inch stacks.
some will say this is a 8 inch exhaust because of the dual 4 inch stacks.
others will say it is a 6 inch because of the dual 3 inch pipes to the stacks. but in truth it is still a 3 inch exhaust, because the turbo outlet, down pipe, and pipe to the splitter was the longest part of the exhaust system, and it was only 3 inch.
the biggest difference of the whole thing was removing the muffler and restriction it caused.
the truck ran the same if it had the full pipes on it or if it only had 6 inches of pipe out of the turbo.
in fact i think it ran a bit better with the pipes.
for 22 years my 88 had a 3 inch down pipe, to a 3 inch splitter to dual 4 inch stacks.
some will say this is a 8 inch exhaust because of the dual 4 inch stacks.
others will say it is a 6 inch because of the dual 3 inch pipes to the stacks. but in truth it is still a 3 inch exhaust, because the turbo outlet, down pipe, and pipe to the splitter was the longest part of the exhaust system, and it was only 3 inch.
the biggest difference of the whole thing was removing the muffler and restriction it caused.
the truck ran the same if it had the full pipes on it or if it only had 6 inches of pipe out of the turbo.
in fact i think it ran a bit better with the pipes.
Laughing Gas
Joined: Aug 2003
Posts: 919
Likes: 4
From: Newberg Oregon
Fact; cant really go by valve guide specs in the size charts, a proper guide job needs to be finish honed to the proper clearance.
What give the myth of 7.3 guide issues is eventually they wear out and cook the spring then drop the valve. And 6.9s do it too but it takes longer.
Having installed several hundred guides in various heads, you would be amazed how much the size changes when pressed in.
What give the myth of 7.3 guide issues is eventually they wear out and cook the spring then drop the valve. And 6.9s do it too but it takes longer.
Having installed several hundred guides in various heads, you would be amazed how much the size changes when pressed in.
Postmaster
Joined: Aug 2010
Posts: 2,554
Likes: 9
From: Northern Arizona
Fact; cant really go by valve guide specs in the size charts, a proper guide job needs to be finish honed to the proper clearance.
What give the myth of 7.3 guide issues is eventually they wear out and cook the spring then drop the valve. And 6.9s do it too but it takes longer.
Having installed several hundred guides in various heads, you would be amazed how much the size changes when pressed in.
What give the myth of 7.3 guide issues is eventually they wear out and cook the spring then drop the valve. And 6.9s do it too but it takes longer.
Having installed several hundred guides in various heads, you would be amazed how much the size changes when pressed in.
Thread Starter
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Postmaster
Joined: Dec 2004
Posts: 2,941
Likes: 32
From: Maple Valley, WA
It may be disagreed upon here but I haven't had any issues yet with running exhaust out to a 6 inch single stack. I've been seeing that a lot of people over various forums would never think about opening up past a 4inch exhaust, but like I said I'm doing just fine going up to six (most if the exhaust is comprised of the 4inch; its the cheapo flex pipe mess).
I went this route because the boys who owned the truck before me ran 5 inch dual stacks, so the bed was already cut into. They even used a 4inch tip as an adaptor!!!. My buddy had a spare 6inch stack he never used, so I just put it up on my truck and made it work.
Exhaust velocity is just fine, and the truck sounds great. I love driving it from a stop because it literally sounds like a boat
I went this route because the boys who owned the truck before me ran 5 inch dual stacks, so the bed was already cut into. They even used a 4inch tip as an adaptor!!!
. My buddy had a spare 6inch stack he never used, so I just put it up on my truck and made it work. Exhaust velocity is just fine, and the truck sounds great. I love driving it from a stop because it literally sounds like a boat
there is a big difference between a 3 inch downpipe, 3 or 4 inch pipes back to a 6 inch stack and a 5 or 6 inch downpipe and exhaust.
for 22 years my 88 had a 3 inch down pipe, to a 3 inch splitter to dual 4 inch stacks.
some will say this is a 8 inch exhaust because of the dual 4 inch stacks.
others will say it is a 6 inch because of the dual 3 inch pipes to the stacks. but in truth it is still a 3 inch exhaust, because the turbo outlet, down pipe, and pipe to the splitter was the longest part of the exhaust system, and it was only 3 inch.
the biggest difference of the whole thing was removing the muffler and restriction it caused.
the truck ran the same if it had the full pipes on it or if it only had 6 inches of pipe out of the turbo.
in fact i think it ran a bit better with the pipes.
for 22 years my 88 had a 3 inch down pipe, to a 3 inch splitter to dual 4 inch stacks.
some will say this is a 8 inch exhaust because of the dual 4 inch stacks.
others will say it is a 6 inch because of the dual 3 inch pipes to the stacks. but in truth it is still a 3 inch exhaust, because the turbo outlet, down pipe, and pipe to the splitter was the longest part of the exhaust system, and it was only 3 inch.
the biggest difference of the whole thing was removing the muffler and restriction it caused.
the truck ran the same if it had the full pipes on it or if it only had 6 inches of pipe out of the turbo.
in fact i think it ran a bit better with the pipes.
A 3" DP is sufficient for any IDI... however, bigger wont hurt.
Logistics Pro
Joined: Apr 2005
Posts: 4,221
Likes: 17
It won't blow it up, but it can blow some head gasket(s).
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i ain't rite
Joined: Mar 2005
Posts: 65,601
Likes: 5,628
From: Marlboro Mental Hospital.
my non wastgated banks has a 3 inch turbo outlet to a 3 inch downpipe.
Laughing Gas
Joined: Aug 2003
Posts: 919
Likes: 4
From: Newberg Oregon
Thank-you for that explanation Russ. Any idea why the 7.3 wears out valve guides faster than a 6.9? I would have expected them to be equal in that regard. Also, what is your take on the roller lifters that folks here have gotten from Harland Sharp? Xcite says it should reduce side loading and lead to longer valve train life. I know those custom parts are pretty spendy, but cost effectiveness aside does it seem like a worthy reliability upgrade?
If I could afford roller rockers I would get them, they virtually eliminate lateral loading.
I have used them on many gas engines, and since we have a relatively fast and high lift cam they would be the ticket.
Postmaster
Joined: Aug 2010
Posts: 2,554
Likes: 9
From: Northern Arizona
Dont have any rock solid evidence of why the 7.3 wears more, it could very well be the "improved" seals.
If I could afford roller rockers I would get them, they virtually eliminate lateral loading.
I have used them on many gas engines, and since we have a relatively fast and high lift cam they would be the ticket.
If I could afford roller rockers I would get them, they virtually eliminate lateral loading.
I have used them on many gas engines, and since we have a relatively fast and high lift cam they would be the ticket.
Postmaster
Joined: Aug 2010
Posts: 2,554
Likes: 9
From: Northern Arizona
I'm still not convinced that turbos blow head gaskets. I think it really depends on what turbo you are talking about, the condition of the gaskets and (engine in general), and the type of driving. Sure. If you put a hot pump and a huge turbo on a tired engine you are asking for trouble, but we have seen some members (noteably dirtydiesel and lil red sled) boost the snot out of old tired engines and the HG's held with stock bolts. Conversely, there seem to be many, many head gasket repair threads and questions involving NA engines.
How many "I installed a turbo and my head gasket(s) blew" threads have you seen?
My experience with head gaskets (on gas engines) have almost all been HEAT related in some way or another. With that in mind, adding oxygen with a turbo on a diesel engine will actually lower exhaust gas temps and keep the upper cylinder temperatures lower than when NA. The pressure will be more, but the temps will be less, and with low to moderate boost levels the pressure is not going to kill the HG's.
That said, my build will definitely have studs, but that is because I want it as strong as I can get it, and I generally think that the head bolts are one of the IDI's weaknesses... it does not mean that I buy into the idea that there is a causal relationship between adding a mild-ish turbo and HG failure.
There. Ant hill kicked.
How many "I installed a turbo and my head gasket(s) blew" threads have you seen?
My experience with head gaskets (on gas engines) have almost all been HEAT related in some way or another. With that in mind, adding oxygen with a turbo on a diesel engine will actually lower exhaust gas temps and keep the upper cylinder temperatures lower than when NA. The pressure will be more, but the temps will be less, and with low to moderate boost levels the pressure is not going to kill the HG's.
That said, my build will definitely have studs, but that is because I want it as strong as I can get it, and I generally think that the head bolts are one of the IDI's weaknesses... it does not mean that I buy into the idea that there is a causal relationship between adding a mild-ish turbo and HG failure.
There. Ant hill kicked.
Postmaster
Joined: Aug 2010
Posts: 2,554
Likes: 9
From: Northern Arizona
This is the best info I can give...
Generally it goes like this... The more timing you give it, the better the top end, but the less low end you get...
However, there is a big variable if you are turboed... and that is the size of your turbo itself...
The bigger the turbo (We can even split hairs from here) the more retarded timing you will have to run to get the ***** you want...
With my S362, I saw the best power at 6* BTDC on the dyno, and I was adamant about that timing setup, until I drove and tuned a fellow members truck with an HX35, and it was a dog at 6* compared to 8*+.... It all has to do with the exhaust side of the turbo and how drive pressure has an effect on the wheel...
The best thing you can do, is to just feel it out... Adjust your timing until it has the best drivability, best all around power, don't be afraid to retard it... That's of course if you don't have access to a dyno, that will give you the info you need... I gained 20whp just from tuning timing alone on the dyno, back when I had my turbo cal...
That is the simplistic way of course... There are a lot of things that change the characteristics of an engine... Injector spray duration can determine a lot of things depending on pop pressure, and the duration determines what static timing the setup will work best at... tuning tuning tuning... That's all I got to say... If you don't have the patience for it, don't worry about the platitudes, just run it how it feels...
Generally it goes like this... The more timing you give it, the better the top end, but the less low end you get...
However, there is a big variable if you are turboed... and that is the size of your turbo itself...
The bigger the turbo (We can even split hairs from here) the more retarded timing you will have to run to get the ***** you want...
With my S362, I saw the best power at 6* BTDC on the dyno, and I was adamant about that timing setup, until I drove and tuned a fellow members truck with an HX35, and it was a dog at 6* compared to 8*+.... It all has to do with the exhaust side of the turbo and how drive pressure has an effect on the wheel...
The best thing you can do, is to just feel it out... Adjust your timing until it has the best drivability, best all around power, don't be afraid to retard it... That's of course if you don't have access to a dyno, that will give you the info you need... I gained 20whp just from tuning timing alone on the dyno, back when I had my turbo cal...
That is the simplistic way of course... There are a lot of things that change the characteristics of an engine... Injector spray duration can determine a lot of things depending on pop pressure, and the duration determines what static timing the setup will work best at... tuning tuning tuning... That's all I got to say... If you don't have the patience for it, don't worry about the platitudes, just run it how it feels...