stroke and turbo

R

RedChuck

NAXJA Forum User
Location
Delaware
OK i'm starting planing my build up of a 4.0. i want to turbo. the donor motor needs a rebuild. i was going to go with forged internals. since i'm going with new parts is it worth stroking it at the same time? i was reading http://www.jeep4.0performance.4mg.com/stroker.html
and if i did the 4.6L low-buck stroker
Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Keith Black IC944-030 pistons
9.6:1 CR
264hp @ 4900rpm, 324lbft @ 3500rpm

it would have great power at idle. and just get better from there. on forged internals bring it up to maybe 10.5-11:1 CR would bring out the devil.

any thoughts? i have never seen both on an engine. does anyone sees any down fall with this setup? how much compression could i run before i would start having failures? would i have any issues using the stock 4.2l crank? please advice
 
Your proposed stroker build should work great but if you're going to add a turbo, I suggest you keep the 9.6:1 CR and limit boost to ~6psi. It'll be a beast!
The 4.2 crank will be fine as long as you keep the stock rev limiter but if funds allow, you could have the journals nitride hardened to add durability.
 
A Supercharger will give you quicker response over a Turbo. In any event, you need to keep the CR down to, in my opinion, no more than 9.6:1. You are at sea level? 6spig of boost is easily attainable and the engine will run for ever (well... at least as long as without FI) while delivering good performance. See www.boostecus.com for a turn key system. The 97 XJ test bed does 0 to 100 in about 17 seconds. This performance is on a 4.0 with 142,000+ miles on it. Better than 11,000 of them boosted...

You Tube Video:
http://www.youtube.com/watch?v=zdgCxNtDZKI
 
I'm helping my brother build a forged 4.9l stroker that'll get a turbo in it's future. The SCR is a low 8.75:1 so that it can see double-digits of boost. Yes, if you have to rebuild the 4.0, then you might as well stroke it in the process. If you go over to pirate4x4.com, you'll be able to read about turbo'd strokers.
 
o-gauge-steamer said:
A Supercharger will give you quicker response over a Turbo. In any event, you need to keep the CR down to, in my opinion, no more than 9.6:1. You are at sea level? 6spig of boost is easily attainable and the engine will run for ever (well... at least as long as without FI) while delivering good performance. See www.boostecus.com for a turn key system. The 97 XJ test bed does 0 to 100 in about 17 seconds. This performance is on a 4.0 with 142,000+ miles on it. Better than 11,000 of them boosted...

You Tube Video:
http://www.youtube.com/watch?v=zdgCxNtDZKI
Click to expand...

I'll be honest, if I were to build a boosted stroker, I'd be really torn between the blower set up you guys have and boostwerks turbo set up. Both would work well under all conditions, but you guys would have the potential to make a boatload of torque now where the turbo would have to rely on the stroker's natural grunt to get over the turbo lag which would have advantages in daily driver traffic situations. One advantage that I can see for the turbo set up is that you can vary the boost based on what octane fuel you have available (making it a flex fuel vehicle) and that could allow you to experiment with anything from 87 octane pump gas to unleaded race gas with some adjustment of the boost controller. If I had the money to do something like that, I'd hopefully have the cash to build two trucks, each one with a different form of Forced Induction.
 
The Bulltear pistons do look good. It would be a good option for you as you can specify the dish size to achieve the compression you want. I haven't heard of anyone using them yet though.
 
When it comes to Forced Induction, I can see both sides of the solutions. Both systems have advantages and disadvantages over the other.

SCs will give boost instantly but require HP to drive them. Boost levels can be controlled with pulley diameter. Also the bypass can be tuned to reduce boost. The Sprintex system actually recirculates air through the manifold/SC combination.

Turbos take time to spool up but the FI is essentially "free" as you are getting a use out of what otherwise just gets thrown away. You have choices to make on turbine/compressor combinations. Remember that bigger is not always better when it comes to Turbos. The more mass you have to accelerate the greater the lag.

Your decision is exactly that. Your decision. Where do you want the power? Money is a secondary issue when pursuing power.

My last XJ (a 97) had a Golen stroker with an Alabama Cylinder Heads aluminium head (1.94/2.02 valves) and I ran a 68mm TB from the 4.7 V-8. Made a ton of torque and hp. Spendy though...


In any event, keep the cranking compression down and have fun!
 
bjoehandley said:
I'll be honest, if I were to build a boosted stroker, I'd be really torn between the blower set up you guys have and boostwerks turbo set up. Both would work well under all conditions, but you guys would have the potential to make a boatload of torque now where the turbo would have to rely on the stroker's natural grunt to get over the turbo lag which would have advantages in daily driver traffic situations.
Click to expand...

If you choose a smaller turbo you can have full boost come in as early as 2000rpm. A turbo from a 3.0L I6 Toyota Supra would be just about the perfect size for a 4.6 stroker.
 
Dr. Dyno said:
If you choose a smaller turbo you can have full boost come in as early as 2000rpm. A turbo from a 3.0L I6 Toyota Supra would be just about the perfect size for a 4.6 stroker.
Click to expand...
I've had some experiance in this arena with my last two cars, I'd still go with the bigger turbo and let the displacement handle things down low.
 
Anyone that has taken a ride in my XJ can confirm that there is very little lag, and It's a large 500whp turbo on a stock 4.0. It's also worth noting that a small amount of lag is also a good thing allowing you to stay out of boost thus saving fuel.

IMO I would definetly keep the static CR around 8:1 due to the Iron head. Keep in mind your not working with a modern all aluminum engine with a high flowing cylinder head which can get away with a higher CR + Boost + pump gas. The iron head absorbs more heat instead of disipating it quickly like an aluminum head which can and will lead to pre-ignition. It's better to the keep the CR low in this case to allow you to tune it for pump gas, rather than find out the hard way you have to run 110 sunoco just to get it out of the garage.
 
Boostwerks.com said:
Anyone that has taken a ride in my XJ can confirm that there is very little lag, and It's a large 500whp turbo on a stock 4.0. It's also worth noting that a small amount of lag is also a good thing allowing you to stay out of boost thus saving fuel.
Click to expand...

That's some of what I had been figuring too, a normal 4.0l at lower altitudes pulls strong enough that it could nicely cover any lag, let alone a stroker, then if you could stay out of the boost, mileage would be pretty decent too!

Boostwerks.com said:
IMO I would definetly keep the static CR around 8:1 due to the Iron head. Keep in mind your not working with a modern all aluminum engine with a high flowing cylinder head which can get away with a higher CR + Boost + pump gas. The iron head absorbs more heat instead of disipating it quickly like an aluminum head which can and will lead to pre-ignition. It's better to the keep the CR low in this case to allow you to tune it for pump gas, rather than find out the hard way you have to run 110 sunoco just to get it out of the garage.
Click to expand...

Good point, the turbo cars I had experience with were Chrysler's mid 80's 2.2 Turbo's with the aluminum head and nickle-iron alloy block and I think those still were 8.5:1 or lower (been too long, I can't remember for sure any more:dunno: )
 
Ok, I want to make it perfectly clear that I am not knocking Turbos, not even close. My experience with the Sprintex SC is my first blush with FI that is NOT Turbo based. Turbos actually appeal to me as they are as close to a something for nothing as you will ever see.

In 1974, when I was in the Air Force, my room mate worked in the engine shop. I was a Repair and Reclamation specialist. As turbos were readily available we added one to his 1971 Datsun 240Z. What a screamer. Thing was... The turbines and the compressors have extremely demanding tolerances in order to be flown. Units that failed were no longer flight worthy. On the other hand, they worked just fine bolted to the side of a car engine... We did by Triumph and we also did several domestic V-8s using twin setups. These were all blow through carburetor installations which required raising rate fuel pressure regulators and electric fuel pumps.

I was just attempting to point out the differences. Everything has plusses and minuses and it would be irresponsible for me think or claim otherwise. Boostwerks manifold is a thing of beauty.

The other point I was attempting was that the lower your Cranking Compression, the higher boost you can run. Most of my FI experience has required the use of copper o-rings to hold the cylinder pressure. There will come a point where you blow out a standard gasket. I have been given to understand that there is a solid copper head gasket available for the 4.0. I'll chase that and report back.

What do you guys think of the aluminium head that is sold by Hesco. They are (were...) made by Alabama Cylinder Head. I bought one from ACH back in 2000 for my 4.7. Made a huge difference. Last I looked at the ACH web site, ACH no longer admits to making the head. Maybe Hesco clamped down?
 
I thought Patriot Performance originally made the head that Hesco bought the rights/tooling to(then proceded to jack the price from $1200-1400 up to $2K).
 
i don't think i am going to go with the SC. if it was a primary trail truck then i would probably go that direction. but staying out of boost when cursing plus i think its cheaper to build a turbo setup.

i had not considered the head retaining heat so i will have to think about that one.

i think thoughts of cams or injectors are still a little far off
 
Now this may sound crazy but what would be pretty cool is dual charging it with an aluminum head. Boostec sc with boostwerks turbo set up great off idle and can build boost. Would take some good thinking though plus we have a pretty small rpm range hut still would be cool. Only problem with a sc and blower is loss of boost due to increased displacement. There was a guy on jeepforum running an avenger kit with 9lb on stock displacement. Then he stroked it and his 9lb pulley only got him 3lb plus there is a point where the sc becomes the restricting point. But either way turbo or sc it's awsome
 
gradon said:
I thought Patriot Performance originally made the head that Hesco bought the rights/tooling to(then proceded to jack the price from $1200-1400 up to $2K).
Click to expand...

That is what I thought as well.
 
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