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Discussion Starter #1
I have been doing research on turboing a D15B7 and have seen were people have had success running 5 -7 PSI boost with a small turbo. Outside of that there is not a lot of info out there.

I have a Y8 head I want to put on my B7 and then add a T3 turbo from a thunderbird . I think it is similar to a T3 60 trim. My question is do you think the stock rods will hold up at 5 – 7 lbs of boost?

The compression would be 10.5 to 1 - 11.00 to 1 depending on the head gasket I use.
 

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Its not the psi its the hp and tq.
The d15 rods will bend sooner then a z6 or y7/8
So with that in mind im going to say that the d15b max power on stock is around 180hp.
x eleventybiliion!!!!!!!!

Some have seen 200 but I wouldn't try it unless you don't care or have a freshly rebuilt and broken in motor.
 

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Discussion Starter #4
i understand that horsepower and torque are the issue. what I am having trouble understanding where I will be with the new head. If I use the 1lb per 10hp original engine is 100hp and 7lb boost would be 170 hp. how much more would the new head add.
 

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With that low of a goal your head isn't going to allow more hp per se. It's ging to bump your compression up. You'll have a lil more fun out of boost. Your weak point is going to be your rods. Those are what's going to hold you back from making more power. Your head is fine.
 

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i understand that horsepower and torque are the issue. what I am having trouble understanding where I will be with the new head. If I use the 1lb per 10hp original engine is 100hp and 7lb boost would be 170 hp. how much more would the new head add.
No disrespect but with formulas like that you shouldnt be boosting.
You can not set a psi to hp out formulas. There are to may things to calac in.
First off a mid size t3 at 5psi may out put the same amount of power as a t25 at 8psi. Thats all im going to say on that do some homework.

Second. You dont need to know what power your at or what the head will output. Get it dyno with the turbo on and everything running.
Back boost down till the graph levels off at around 180hp and call it a day.


Your a noob to boost and there is alot that goes on with boosting a car and tons of things that can go wrong and mess up the motor.

In order to find out the information you want to know. You need to look up other people setups and see what hp they made on "x" turbo and "y" psi.
Then you start comparing. Your end up with a graph that will let you know what turbo will make "z" amount of hp on your setup.

And fyi a mini-me normally outputs around 130hp because of bump in comp

Also a small t25 is probably what you want if your keeping the motor stock. You dont want to be out of the turbos range, or spooling late in the rpms.
 

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well I have the same set up except a y7 head and I am also getting ready to boost it but I have taken a few preventive measures. I have installed arp rod bolts and head suds and the motor is freshly rebuilt and broken in it has 15k miles on it now no problems. the t bird turbo is small it a 42 compressor 48 or 63 a/r exhaust depending on what year car it came off of

With that turbo you should be ok up to about 10 psi that should be what it take to make 200hp. If you have a careful tuner I would start around 6 or 7psi and work up from there also what is you rev limit going to be because this plays a big role in how much stress goes into the rods. Tops I would do is 7000 with arp rod bolts 6500 with out.

The turbo I'm going to use is a true 60 trim 63 a/r exhaust precision single ball bearing this I know is capable of blowing my engine up. My tuner told me that we should be able to run between 6 and 8 psi all day no problems because he had a 200 dollor high mileage d15b7 stocker running about 220 to 250 hp at 7200 out of a ebay 50 63 a/r exhaust at 10or 11psi with no problems for a couple of weeks but it wasn't his fault the kid with the car kept wanting more each week so he warned him and they took it to the edge and it broke during a 4th gear pull on the street at about 140mph.
 

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Discussion Starter #9
puts me very close to the 200hp mark. what effect will the higher initial compression have on the rods.
 

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puts me very close to the 200hp mark. what effect will the higher initial compression have on the rods.
again it doesnt matter directly, it will only be a problem for timing and gas.
Its the tq that breaks stuff.

Ill break it down for you.
The piston comes up to top dead center (tdc). Sparks, and we have combustion, which slams that pistons down. (your motor really is a control bomb).

Now the force that throw that piston down is your tq. And if you look at a dyno your see it plotted as a curve. This is called your tq curve. That is what bends/breaks the rods.
If your car is going from 80hp to 200hp in a matter of seconds. Those pistons are being throw down with so much force that they just cant keep up and they bend.

With that said. When a d15 hits around 200hp the piston are being force down with all that power and they start to bend because they just cant take it.
Its like a metal pipe. You can hit it on a wall all day long and probably never bend it. BUT if you put it in a vise and hit it with a hammer its going to bend. Same thing here.


So yea it doesnt matter what your comp is, if your boosting or N/A. Its all about the tq curve it makes. i.e why NOS messes up things faster then boost. The spray comes on and spikes the tq curve.
 

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It won't have to much effect on the rods just on the amount of timing you can put into the engine with out proper fuel to keep down on detonation. RPM is the a big factor because it puts more stress on the rod then boost.

What my tuner told me what broke the kids car was when he turn the rev limiter from 6800 to 7200rpm because the car had been at 10 psi on the ebay 50 trim for a couple of weeks and several times down the track with no problems. He said after I maxed out the stock map sensor all i could do was turn the rpm up to make more power but after I did that it only lasted a couple of days before it broke.
 

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It won't have to much effect on the rods just on the amount of timing you can put into the engine with out proper fuel to keep down on detonation. RPM is the a big factor because it puts more stress on the rod then boost.

What my tuner told me what broke the kids car was when he turn the rev limiter from 6800 to 7200rpm because the car had been at 10 psi on the ebay 50 trim for a couple of weeks and several times down the track with no problems. He said after I maxed out the stock map sensor all i could do was turn the rpm up to make more power but after I did that it only lasted a couple of days before it broke.
Not saying what your saying is a lie but i think. You had a boost spike and the extra power and untune for the higher psi broke the car.
I heard of and seen people red line there boosted car with no harm done.
 

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Discussion Starter #13
I know I am using rough rule of thumb, and yes I am new to turbo, not performance engines. not really looking to push this engine real hard. just want to learn more about turbo and tuning OBD1. I am more aware than most about the many calculations to determine power with a turbo. I understand compressor area versus volume and that larger compressors flow more air at a given PSI. that is why I indicated what turbo I have. I believe the compressor and turbine housing are both .63 AR hsgs, I was just looking to hear from some guys real world experience with turbo on stk D15B7 engine. I have another B7 engine and forged FJ rods that I will build and boost to around 20psi when I learn everthing I want with this first engine. just have to develop a good plan to deal with Vitara piston low ass compression. My Y8 head is part of that solution.
 

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I wasn't say red lining is what killed it. what I was saying is at that power level on these engines a little more RPM can Kill. Just think about it, why would they put thicker rods in a b16 and type R engine then any other B series engine when both have better rod ratios. We also know of people with high compression d series engines revving just as high on stock rods with no problem but there power level is not as high a boosted engine. The reason why Honda put thicker rods is because rpm puts some kind of stress on the rods.
 

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I know I am using rough rule of thumb, and yes I am new to turbo, not performance engines. not really looking to push this engine real hard. just want to learn more about turbo and tuning OBD1. I am more aware than most about the many calculations to determine power with a turbo. I understand compressor area versus volume and that larger compressors flow more air at a given PSI. that is why I indicated what turbo I have. I believe the compressor and turbine housing are both .63 AR hsgs, I was just looking to hear from some guys real world experience with turbo on stk D15B7 engine. I have another B7 engine and forged FJ rods that I will build and boost to around 20psi when I learn everthing I want with this first engine. just have to develop a good plan to deal with Vitara piston low ass compression. My Y8 head is part of that solution.
That's a good way to go about it but I would stay away from a y8 head on a boosted motor. The quench zones on that head don't work as well for a boost because the can cause detonation I would use a plane y7 or z6 head with the more open combustion chamber. The FJ rods were set up to put the vitaras at the top of the deck to increase the compression ratio to an acceptable level.

P.S.
Question? Do you know the exact length of the FJ rods for the d15b2/7 I'm just curious. I played with some numbers on zealautowork but I would like a exact number to make my math more accurate
 

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boost with what you have and save your money. I'm going to turbo my setup next month if you want to wait and see for yourself :)
 

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There are a shit ton of people who have boosted B7 motors. Check out real hmt or hmt. (Home made Turbo) Its been done so many times that all you really need to do is make sure your motor is healthy, buy or peice a kit together and tune it. Xile knows his stuff. He's pretty much laid it all out for you. The spoon doesn't get much closer to your mouth.....

Sent from BigJ's Mobile Awesome Device
 

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Discussion Starter #18
That's a good way to go about it but I would stay away from a y8 head on a boosted motor. The quench zones on that head don't work as well for a boost because the can cause detonation I would use a plane y7 or z6 head with the more open combustion chamber. The FJ rods were set up to put the vitaras at the top of the deck to increase the compression ratio to an acceptable level.

P.S.
Question? Do you know the exact length of the FJ rods for the d15b2/7 I'm just curious. I played with some numbers on zealautowork but I would like a exact number to make my math more accurate

Have not measured them myself, but when I bought them they were advertised as 136.4mm
 

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That's a good way to go about it but I would stay away from a y8 head on a boosted motor. The quench zones on that head don't work as well for a boost because the can cause detonation I would use a plane y7 or z6 head with the more open combustion chamber. The FJ rods were set up to put the vitaras at the top of the deck to increase the compression ratio to an acceptable level.
Wrong. Flat out, plain wrong. Quench zones in the Y8 head with the flat top B7 pistons will not cause detonation. What will cause detonation is running too much timing advance with a mini-me combo of the Y8 head and B7 block. Even stock Z6 timing maps WILL cause detonation, even if you dial back the initial timing to the proper 12*BTDC for the Y8 head.

This combo is very dangerous because it creates a VERY fast burn combustion event and you MUST make sure that your timing advance is very, very conservative or you WILL bend a rod or crack a ring land faster than a fat kid on a birthday cake.
 

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Discussion Starter #20
Those were my thoughts exactly it is a function of timing not combustion chamber design. As I understand it the tighter quench should produce better fuel mixing and lead to better efficiency and improved detonation resistance.

I am glad someone came along and verified this for me.
 
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