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HT4100 4.1, 4.5, 4.9 Discussion, The "4.9 liter turbocharger, stage 1" thread. in Cadillac Engine Technical Discussion; yeah thats cool.. to lower the compression, youd want to get some quad-4 pistons, they fit and will give you ...
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    Re: The "4.9 liter turbocharger, stage 1" thread.

    yeah thats cool.. to lower the compression, youd want to get some quad-4 pistons, they fit and will give you about 9:1, of course getting some head work done will lower it slightly more, 8.6-7 to 1, thereabouts.. I woudl HIGHLY recommend geting LT1 1.94 in. intake valves for this when you get the head work done.. get new exhaust valves too
    but for a 12 valve 6 cyl 3.8 buick...order them new

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    Re: The "4.9 liter turbocharger, stage 1" thread.

    An odd thing with turbo engines I have noticed over the years. They all seem to have small valves. I have never seen a factory production turbo with large valves.

    My 301 Turbo: 1.75 Intake 1.5 Exhaust (my particular car, 290 RWHP)
    GN Turbo: 1.75 Intake, 1.5 Exhaust (245HP stock, easily to make 400+ with stock long block)

    Honestly, with the boost, valve size may not matter at all. I guess if you are going all out, 15+ psi boost, sure, the valve will become a restriction to the flow, raising boost when it shouldn't be (backpressure in the intake tract will make the turbo back up and activate the wastegate early, thus lowering overall cylinder boost pressures)

    Maybe increase exhaust valves on the exhaust, but until boost gets up, don't mess with them. BUT, OTOH, boosted engines often have sodium filled exhaust valves. The 301, not sure, they are fat suckers, enough room they probably do, the 3.8L Supercharged Ford, the 2.3L Turbo Ford, both do. Not sure on GN, probably does.

    So, do consder that. If you are swapping valves, look for the necked down valves that have more flow around the valve, but keep with the Severe Duty versions if at all possible. Turbocharging is serious business. (more for Phase 2 not Phase 1) High mileage valves can be a risk.

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    Re: The "4.9 liter turbocharger, stage 1" thread.

    The largest intake vlaves the 4.9L heads will handle are 1.94 intake valves, and keep the same size stock exhaust valves, 1.50

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    Re: The "4.9 liter turbocharger, stage 1" thread.

    of course, you could always go for the biggest normally aspirated 4.9L ever! hehehe... if you shave the heads .050, and use Northstar pistons ( use the stock sleeves, just have them bored .040 ), you'll get in the neghborhood somewhere of 11.5 to 12:1 compression.. of course, pump gas is useless at this compression unless you use a different ECM entirely, one with a knock sensor of course..have a custom built valvetrain, and a very high lift cam...

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    Re: The "4.9 liter turbocharger, stage 1" thread.

    I am not that familliar with the dimensions of the Quad 4 pistons, but you don't want to mess up the quench. You can mess with the other side, but the quench area is cruicial to helping manage and eliminating pinging. Typically around 0.040". Alum rods increases that by around 0.040 to 0.080. And if it has 4 valve relief's, are they in the correct position for the 4.9L? Same with N* pistons. BEing the 4.9L shares pistons with the 3.4L Chevy V6, pistons and rings should be plentiful and cheap. Sick puppies like me read websites like KB-Silvolite.com. It is interesting to find out what works with what...

    Quote Originally Posted by stickpony
    yeah thats cool.. to lower the compression, youd want to get some quad-4 pistons, they fit and will give you about 9:1, of course getting some head work done will lower it slightly more, 8.6-7 to 1, thereabouts.. I woudl HIGHLY recommend geting LT1 1.94 in. intake valves for this when you get the head work done.. get new exhaust valves too
    but for a 12 valve 6 cyl 3.8 buick...order them new

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    Re: The "4.9 liter turbocharger, stage 1" thread.

    You know what I've just realized? We're getting nowhere fast with this project! There has been about 140 posts pertaining to pistons and camshaft changes that I will not use at all for stage 1

    Let's get back to topic here and start to figure things out. I mean Christ, it's just another engine with the same characteristics that almost every other V8 has in terms of moving parts...So I'm not getting all fancy. It's just a tune before the real deal if you please...

    Ok, for stage 1:

    a.) No intercooling whatsoever. Tom has stated time and again that for 6 simple psi that it won't be needed.

    b.) Fuel. I'm just going to order the Megasquirt self-programmable system and get with it. I have most of what I need and will run with an auxiliary TBI system to add more fuel. I'll add the extra fuel pump and lines too.

    c.) Timing. So I'll keep factory settings of 10 for idle. The MSD boost timing controll can take care of the rest.

    d.) Turbocharger. I would like to have the compressor map done, but I really feel that the turbo I have will suffice for now.

    e.) Tubing and pipes. I'm installing the turbo via the crossover pipe from a Deville. There will be Deville front and rear exhaust manifolds feeding the crossover pipe, which will in turn feed the turbocharger.

    f.) Boost level controls and a blow-off valve. Done. The turbo I have has a dual-port wastegate system and the boost control should work out fine.

    All that is really needed is for me to order the Megasquirt and build it. Welding pipes and other things together is easy. Or at least I hope so.

    Okay people, let's get with it here. If I'm going to blow this thing up, let's do it in style!!!

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    Re: The "4.9 liter turbocharger, stage 1" thread.

    Funny you should mention it, I was actually looking at the title to the thread last night, thinking, we are not posting at all about Stage 1! But the bunny trails were cruising on and on....

    You are right, the MSD BTM and 4-6 psi boost to start (keep boost low initially) with a simple mechanical wastegate, unless we have $$ to get an electronic one and make a knob inside the car (which would be nice to help save the engine if boost is suddenly too high, maybe make an ESC module control the wastegate instead of the timing control) A way to monitor pinging should be seriously considered. GM put knock sensors (ESC) on 3.8L's, Turbo 301's, and various other cars. Look for G Bodies with V6's and the ESC module is on the pass side fender. Snag a few of them. Get some various knock sensors, 4.6L N*, 2.8L Chevy (if they have), 3800, 3.8L, 3300, 1.8L Turbo 4, 2.0L Turbo 4, etc. You may need to experiement with the one that is most sensitive. Install them one in each block coolant drain. Closer to the cyls is best. Becareful removing those drains! It is an aluminum block, so it might not come out easily.

    Plan out where the turbo can do, how to get exhaust to it and away from it (likely on top of the trans, that is where Pontiac put it on the 1988 SSE Turbo Bonneville prototype), obviously the air box is removed, build an abundance of heat shields you WILL need them, a little goes a long way on a heat shield. You can drop temps 50 degrees with 1/2" air between the source and the thing you are protecting.

    Calculate the boosted airflow requirements. If the turbo is at 14.7 psi, you are double the CID. Make sure the TBI unit will flow enough air for you, at 7.5 psi you are ballpark 450 cid. You may need a 454 unit, stock maybe, maybe a little porting. You don't want it to be a boost restriction and having it backing up the intake tract. I need to look at the allante intake more (is that Stage 1 or 2?). Make sure there is some plenum under the TBI. Being the 4.9L isn't a high revver, the 454 TBI is probably sufficient, for stage 1....

    I am wondering if the MS is best saved for Stage 2 and use my idea to trigger extra fuel for stage 1. Simple, cheap, and very effective.

    Does anyone know if the Cadillac PCM will handle a 3 bar MAP? And has anyone broke the programming on it? Does anyone have any friends at GM in handware or software engineering that might be willing to answer silly questions like that?

    You should not need anything special on wastegate with that low boost. Like an extra exhaust pipe, etc.

    When I was pondering turboing my 3800, I was looking at bringing up the exhaust to the turbo right off the factory crossover, and then return it back to the cat converter in the stock pipe with an extention. Just weld off that nasty back side crossover on the 3800. (Thrasher Engineering makes a replacment that isn't so bad, for you guys with a 3800) Odd thing, the 3800 has a 2.3" crossover pipe, the 4.9L is smaller, like a 2" or 1.75". Maybe you can adapt the 3800's pipe.

    Oil supply, oil pressure sending units with a T work, but not always sufficent flow. The closer you get to the oilpump the better. If you can up oil pressure, DO SO! Oil drain back. Drain must be lower than turbo exit. The intake may work, you might need to drill a hole in the backside of the intake to drain into the lifter valley.

    Being we already have an engine oil cooler, that is good. Either monitor oil temps or go synthetic. Even with me changing oil very often, the oil didn't survive enough to save my rod bearings. So it is low cost bearing insurance. 15W40 may be sufficient though.

    Turbos LOVE cooling engines and cold air induction. A cold day will give you a ton more power than a warm day.

    Insulate the exhaust pipes going up to the turbo. Spools faster and reduces underhood heat. But, non stainless pipes may not live as long.

  8. #143
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    Re: The "4.9 liter turbocharger, stage 1" thread.

    Quote Originally Posted by N0DIH
    Funny you should mention it, I was actually looking at the title to the thread last night, thinking, we are not posting at all about Stage 1! But the bunny trails were cruising on and on....

    You are right, the MSD BTM and 4-6 psi boost to start (keep boost low initially) with a simple mechanical wastegate, unless we have $$ to get an electronic one and make a knob inside the car (which would be nice to help save the engine if boost is suddenly too high, maybe make an ESC module control the wastegate instead of the timing control) A way to monitor pinging should be seriously considered. GM put knock sensors (ESC) on 3.8L's, Turbo 301's, and various other cars. Look for G Bodies with V6's and the ESC module is on the pass side fender. Snag a few of them. Get some various knock sensors, 4.6L N*, 2.8L Chevy (if they have), 3800, 3.8L, 3300, 1.8L Turbo 4, 2.0L Turbo 4, etc. You may need to experiement with the one that is most sensitive. Install them one in each block coolant drain. Closer to the cyls is best. Becareful removing those drains! It is an aluminum block, so it might not come out easily.

    Plan out where the turbo can do, how to get exhaust to it and away from it (likely on top of the trans, that is where Pontiac put it on the 1988 SSE Turbo Bonneville prototype), obviously the air box is removed, build an abundance of heat shields you WILL need them, a little goes a long way on a heat shield. You can drop temps 50 degrees with 1/2" air between the source and the thing you are protecting.

    Calculate the boosted airflow requirements. If the turbo is at 14.7 psi, you are double the CID. Make sure the TBI unit will flow enough air for you, at 7.5 psi you are ballpark 450 cid. You may need a 454 unit, stock maybe, maybe a little porting. You don't want it to be a boost restriction and having it backing up the intake tract. I need to look at the allante intake more (is that Stage 1 or 2?). Make sure there is some plenum under the TBI. Being the 4.9L isn't a high revver, the 454 TBI is probably sufficient, for stage 1....

    I am wondering if the MS is best saved for Stage 2 and use my idea to trigger extra fuel for stage 1. Simple, cheap, and very effective.

    Does anyone know if the Cadillac PCM will handle a 3 bar MAP? And has anyone broke the programming on it? Does anyone have any friends at GM in handware or software engineering that might be willing to answer silly questions like that?

    You should not need anything special on wastegate with that low boost. Like an extra exhaust pipe, etc.

    When I was pondering turboing my 3800, I was looking at bringing up the exhaust to the turbo right off the factory crossover, and then return it back to the cat converter in the stock pipe with an extention. Just weld off that nasty back side crossover on the 3800. (Thrasher Engineering makes a replacment that isn't so bad, for you guys with a 3800) Odd thing, the 3800 has a 2.3" crossover pipe, the 4.9L is smaller, like a 2" or 1.75". Maybe you can adapt the 3800's pipe.

    Oil supply, oil pressure sending units with a T work, but not always sufficent flow. The closer you get to the oilpump the better. If you can up oil pressure, DO SO! Oil drain back. Drain must be lower than turbo exit. The intake may work, you might need to drill a hole in the backside of the intake to drain into the lifter valley.

    Being we already have an engine oil cooler, that is good. Either monitor oil temps or go synthetic. Even with me changing oil very often, the oil didn't survive enough to save my rod bearings. So it is low cost bearing insurance. 15W40 may be sufficient though.

    Turbos LOVE cooling engines and cold air induction. A cold day will give you a ton more power than a warm day.

    Insulate the exhaust pipes going up to the turbo. Spools faster and reduces underhood heat. But, non stainless pipes may not live as long.

    Thanks again for the info Tom. I am sorry if I sounded like a jerk with my last post, which was not singling anyone out, I was just a little buzzed and was wondering where I am getting with this project I have been promising for close to a year now...

    I was checking out that 4.9 buildup thread and I seen the most interesting thing that I would like to use. They had a set of 4.1 liter exhaust manifolds in the picture that appear to be stainless, and they are the same material that I have on my '87 Seville, only those are made for the cross-under pipes. I'm just not too sure how the flow would work out should I decide to use those instead of the cast iron manifolds. I have a set of Deville exhaust manifolds laying around along with a cross-over, but they seem to be the cast iron manifolds. The cross-over is stainless I believe...I would much prefer the header look of the 4.1 liter manifolds as well.

  9. #144
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    Re: The "4.9 liter turbocharger, stage 1" thread.

    Absolutely not, I agree, we got off on some good bunny trails thought! I think we all tend to go with the flow of the thread, almost Ralphlike...

    I haven't take a look at the 4.1L stainless, if they are like the Olds 5.0L "Y" stainless, they might be a good choise if they are a bolt on. For Olds, they only work on 7A heads with the tiny exhaust ports (althought they DO have the more desired fully divided center 2 exhaust ports, which is rumored to pick up 30 hp on an modifed engine, I would guess more like 15 myself....). A little trick to manifolds is to go too big on headers or manifolds to allow a block to reversion. The exhaust pulse is larger once it gets in the pipe, and then when the pressure pushes it back or the cyl tries to suck it back, the pulse will get partially stopped at the port exit. free power though less diluted chamber. Ok, NOx might go up slightly, but who cares, right?



    Quote Originally Posted by illumina
    Thanks again for the info Tom. I am sorry if I sounded like a jerk with my last post, which was not singling anyone out, I was just a little buzzed and was wondering where I am getting with this project I have been promising for close to a year now...

    I was checking out that 4.9 buildup thread and I seen the most interesting thing that I would like to use. They had a set of 4.1 liter exhaust manifolds in the picture that appear to be stainless, and they are the same material that I have on my '87 Seville, only those are made for the cross-under pipes. I'm just not too sure how the flow would work out should I decide to use those instead of the cast iron manifolds. I have a set of Deville exhaust manifolds laying around along with a cross-over, but they seem to be the cast iron manifolds. The cross-over is stainless I believe...I would much prefer the header look of the 4.1 liter manifolds as well.

  10. #145
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    Re: The "4.9 liter turbocharger, stage 1" thread.

    Quote Originally Posted by illumina
    Tom, the reason I was thinking about the Allante intake is the exact reason you've stated: the plenum will help cool the charge air temps...Am I right?

    Also, here is a picture of the combustion chamber from an HT-4100 cylinder head. The 4.5 and 4.9 liter heads are exactly alike in the combustion chambers...

    See what can be done here. There seems to be enough material to lower the compression ratios to your idea of 8.2:1 or so.

    Let me ask you this as well: you stated that the lower compression ratio would'nt take too much power away. What are the exact losses you would expect if it was lowered to 8.2:1? If we are dealing with an engine with a higher lift cam, roller rockers, Allante intake, and head work (the whole 9 yards on the heads), you're saying that the compression loss would be minimal? Please let me know...

    Here is the picture of the head combustion chamber:

    negative... 4.5L heads from 1990, '89 and later allante engines, and 4.9L engines are the same. 4.5L TBI engiens' heads arent as good

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    Re: The "4.9 liter turbocharger, stage 1" thread.

    Quote Originally Posted by N0DIH
    I am not that familliar with the dimensions of the Quad 4 pistons, but you don't want to mess up the quench. You can mess with the other side, but the quench area is cruicial to helping manage and eliminating pinging. Typically around 0.040". Alum rods increases that by around 0.040 to 0.080. And if it has 4 valve relief's, are they in the correct position for the 4.9L? Same with N* pistons. BEing the 4.9L shares pistons with the 3.4L Chevy V6, pistons and rings should be plentiful and cheap. Sick puppies like me read websites like KB-Silvolite.com. It is interesting to find out what works with what...
    N* pistons are a very common hotrodding upgrade for the 4.9L engines..the "quench" area that you speak of on the N* pistons, 4 concave little etchings on the surface of the piston,is actually notfor that, but to create turbulence in the combustionchamber, which leads to cleaner, more efficient burning for the fuel. I was talking to BUd of Bu'd outback, a specialty shop out in arizona that specializes in hot rodding the 4.9L and N* engines, and he was telling me that gM originally put those concave 1/4-moon shaped etchings on the head around the outside of thevalves, but too many test heads were failing and cracking because of the lack of available space on the head because of having 4 valves per cylinder, so they put them on the pistons instead. anyways.. the N* pistons will actually burn cleaner than the 4.9L pistons. I dont know how well the quad 4 pistons will burn, but i talked with a friend who puts 4.9L engeins in fieros, he did the quad 4 piston swap, and said that the compresison is actually 8.5:1 without head work if you use the quad 4 pistons.

  12. #147
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    Re: The "4.9 liter turbocharger, stage 1" thread.

    Quote Originally Posted by stickpony
    negative... 4.5L heads from 1990, '89 and later allante engines, and 4.9L engines are the same. 4.5L TBI engiens' heads arent as good
    I don't know where you got that I said what heads are better than the other, and I also don't know where you got that either. The picture posted was a sample for Tom to take to his friend, as the head design in the combustion chamber is the same.

    Speaking of which, I don't know if you realize this or not, but the combustion chamber design is the same for all 4.x heads. I have taken enough of them apart and rebuilt them to know this. The only difference between the TBI heads and the MPFI heads are the intake water passage area, and perhaps better oil return from the MPFI heads. It really isn't possible to use the 4.1 liter heads for a MPFI intake manifold because of the water passages. Other than that, they are made of the same material and have the same basic combustion design, which is all that I stated. If you happen to re-read my post before you actually make a statement against it, make sure you get what I said right.

  13. #148
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    Re: The "4.9 liter turbocharger, stage 1" thread.

    Also, though I appreciate the link to the 4.9 buil-up, I am not going to use a single Northstar/Quad-4/whatever piston in this stage, or in stage 2. The information given pertains to an engine being built for natural aspiration, not turbocharging.

    My aim for stage 2 will be to lower compression ratio for more boost, not raising it to blow my engine during boost. So let's consider the Northstar piston upgrade a closed matter and get with what needs to be done for stage 1.

    Thank you

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    Re: The "4.9 liter turbocharger, stage 1" thread.

    IIRC, the N* pistons were close to the 4.9L, but not the same, but I don't remember which way. I'm checking KB-Silvolite.com for more details. Another concern is the valve relief angle. Again, I don't have the details of the 4.6 and 4.9L on this.

    For some serious reading on pistons and engines, take some time and read at http://kb-silvolite.com/ and look for the tech pages. The ones on Quench are very interesting.

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    Re: The "4.9 liter turbocharger, stage 1" thread.

    Here are the details on the pistons:
    http://kb-silvolite.com/spistons.php...tails&S_id=624 for the N*
    and
    http://kb-silvolite.com/spistons.php...tails&S_id=228 for the 4.5L/4.9L

    Interesting, they are 1mm difference in size, and nearly identical everything else. So it would appear they are a decent swap. Comp height is the same, and pin is the same (0.0002 off)

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