Semi-Conventional E85 4.7 Build

[LRSimons]

IMHO :
I woudn't go to .060" over, power gain doesn't amount to squat.
I would also get the engine together and running NA, with a fuel system built for boost on e85, first once the bugs are sorted out, add boost and a megasqurit.

I'm seeing the viability of going only .030 over with the turbo. I think i would for sure go .060 NA, but you are probably correct and adding another pound of boost would add 5x the power compared to the displacement from .030 more bore. Pointless for the extra strength/ peace of mind. The walls are thinner than I expected after I cracked the engine open for the first time, not really sure what I was expecting though.

However, I doubt the cylinder walls bored .060 would be the point of failure if the engine was tuned to the ragged edge. Which, theoretically, with forged and balanced internals, a capable fuel system, and detonation kept at bay with all the tricks- would be more power than would be realistically useful in any environment that I can think of. Besides a dyno

The 35/40 hybrid was single scroll IIRC but the spool was amazing. Came on super quick; almost too quick and hard. It was not very linear, but I learned to drive around that light switch aspect of it. It was probably the must fun the car ever was. The straight 40 was twin scroll and the boost came on mitre gradually as you would imagine. Thing pulled like a freakin freight train up to. It was probably a little north of 600hp at 3.2 bar of boost.

3.2 bar??? As in ~45 psi? Holy cow... that's equivalent to somewhere around a 10 liter NA engine, right? I guess 600 or so sounds realistic when you think about it that way.


Sounds promising. Forgive my ignorance on turbo matters, but are larger turbos such as these efficient/effective at low boost levels? From what I've seen people push 30+ psi on these regularly, as they were designed to do on the diesels they came on. I know large turbos will be more efficient at higher boost, running cooler and all that. But at lowish boost, say 6 lbs on this HX35, would it make sense to run this turbo? A small turbo should spool faster in theory.

Not that I'm that concerned about spool too much. High compression and the twin scroll housing will make it work whether it wants to or not

A note on the twin scroll housing. Current idea is to get one of those weird twisty headers with two collectors and fab two down(up?) pipes to the turbo where a fancy flange will bolt them to the turbo. Thinking the turbo will work best on the passenger side. I know it's been done, but I have no idea if pipes will fit under the oil pan on a stock suspension jeep. Shoulda measured before the engine came out. Oh well. I'm seeing the advantage of a 2WD jeep now.

[SkylinesSuck]

Sorry, typo. 2.2 bar! The test in the morning

[SkylinesSuck]

K, so yeah, 2.2 bar. It was something like 33 psi or something. It was a 2.5L. Holset, just like any turbo, have an efficiency range. You can go above and below it. 6 psi will definitely be below it. These turbos were designed for relatively high boost applications on diesels. IIRC the HX40 compressor didn't start making good power until like 1.2-1.3 bar, and I think the HX35 was similar. If you aren't running that much boost, you might have yourself the wrong turbo. Then again, what are your power and driving goals for it?


I like the idea of staying with a split exhaust going in to each exh housing scroll. Is the firing order of our beloved I6 conducive to feed one scroll 1-2-3 and the other 4-5-6?

[SkylinesSuck]

I just reread your above post. The efficiency at higher boost means airflow vs heat. It will still get hotter as you add more boost. Less boost means a much cooler charge, but also much less air flow. There is a balance. You could run it at 6psi, but it wouldn't make a lot of power, and wouldn't spool as well as a smaller turbo and/or one optimized to run at lower boost. Don't grey stuck on running certain boost numbers though. Lots of people don't have a good understanding of air flow vs boost. 14 psi on "x" engine with "x" turbo does not equal to 14 psi on a different set up. The same applies for different turbos/blowers on the same exact engine at the same boost.

[LRSimons]

I like the idea of staying with a split exhaust going in to each exh housing scroll. Is the firing order of our beloved I6 conducive to feed one scroll 1-2-3 and the other 4-5-6?

Yes. From what I've read, setting up a twin scroll is (more) convenient on an i6 as the optimal combo of cylinders is 123-456.

As I was walking past the factory header(ish) sitting in my driveway waiting to either go out with the trash or get picked up for free, I noticed this-



That's pretty much what I would be looking for in the cool twisty header- ports 123 and 456 combined into individual pipes. Sure the runners aren't equal length and it probably flows crappy, buuuut it's an easy solution and saves some money.

I just reread your above post. The efficiency at higher boost means airflow vs heat. It will still get hotter as you add more boost. Less boost means a much cooler charge, but also much less air flow. There is a balance. You could run it at 6psi, but it wouldn't make a lot of power, and wouldn't spool as well as a smaller turbo and/or one optimized to run at lower boost. Don't grey stuck on running certain boost numbers though. Lots of people don't have a good understanding of air flow vs boost. 14 psi on "x" engine with "x" turbo does not equal to 14 psi on a different set up. The same applies for different turbos/blowers on the same exact engine at the same boost.

Agreed on the cfm vs psi point. I think I understand the theory, but with no actual experience it's difficult for me to wrap my mind around.

K, so yeah, 2.2 bar. It was something like 33 psi or something. It was a 2.5L. Holset, just like any turbo, have an efficiency range. You can go above and below it. 6 psi will definitely be below it. These turbos were designed for relatively high boost applications on diesels. IIRC the HX40 compressor didn't start making good power until like 1.2-1.3 bar, and I think the HX35 was similar. If you aren't running that much boost, you might have yourself the wrong turbo. Then again, what are your power and driving goals for it?

This was the "effectiveness" window I was asking about. Not making good power until 1.2 bar might not work that well for this engine. How would displacement affect this?

Power and driving goals? Hmmm... I guess a healthy amount of reliable, controllable power in a unique format would be what I'm looking for. And being able to beat the redneck lifted truck crowd and the rich kid ricer crowd stoplight to stoplight.

I think I just described a regular Jeep stroker motor.

Power goal? I may as well pick a number. If 200 at the wheels is about what a "normal" stroker makes, a breathed on stroker at 1 bar of boost *should* make about double that. Let's shoot for 350 whp. Should be enough to break some driveline components

[LRSimons]

Forgot to attach pic of the factory exhaust.

[SkylinesSuck]

350whp is no small goal for our vehicles. Did you say it was 2wd though? Anyways, I'd say 1.2-1.5 would be what you need on that turn to get those kind of numbers with that turbo. Just tune it right and intercool it. Maybe a little meth for a safety margin.

[LRSimons]

Negative on the 2wd, I was remarking on how much easier that would make things

Intercooler tubing will probably have to down the sides of the radiator and underneath. Not enough room on the sides to go straight past. That's a long way off though. Cross that bridge when it gets here.



Cut off the end of the stock manifold- The tubes are D-shaped rather than circular. Have a look. Turbo flange for comparison.

[LRSimons]

Ordering parts. Would the Comp 68-232-4 be a bad cam choice for any reason? I think it sounds like a good compromise between stock and crazy as I stated a while back.

Just want to make sure I get any relevant opinions before I hit the button.


Also, has anyone used an oil pump rebuild kit? The price is right and it's not like the housing itself is going to wear out...

[Russ Pottenger]

Are you doing a valve spring upgrade?

[LRSimons]

From what I've heard a valve spring upgrade is necessary for this cam.

From what I've read, a lower spring pressure might work with significantly lighter than stock valves. I have not found any but haven't looked that hard.

So, yes to stiffer springs.

[Russ Pottenger]

From what I've heard a valve spring upgrade is necessary for this cam.

From what I've read, a lower spring pressure might work with significantly lighter than stock valves. I have not found any but haven't looked that hard.

So, yes to stiffer springs.

The most important issue is the valve spring relationship to lift and coil bind.

Just wanted you to be aware that Comp's 68-232-4 cam is right at the limit of a stock spring.

[LRSimons]

Okay, it's been a while. Time for some updates.



First off, I DROVE the jeep for the first time in over 3 months the other day!


It was totally awesome.




However

It doesn't have a fire breathing turbo stroker yet.


I made the call to pick up a craigslist 4.0, and I'm glad I did. I expect that this will be a very worthwhile investment.

-I've now actually removed/replaced a jeep engine now. A little practice goes a long way. It would have been bad to play with my nice new (future) engine without this experience.
-One of the other vehicles can be sold with the jeep operating at full capacity, funding this project
-I can set up MS and the turbo on an engine I don't care about and make all the mistakes I need
-I've never done a glory pass before. Once everything is set up and the rebuild engine can go in, we can find out how much nitrous/boost a stock 4.0 will take!


The jeep has a few kinks yet (not charging, clutch barely disengages despite a firm pedal, blower fan doesn't work) before it's ready for the fun stuff.


Seems like my build is happening in the reverse order of what I originally planned. First order of business once the heep is roadworthy is mounting the turbo. I would like to figure this out now rather than later as it's probably going to be a mess either way. I can't wait to make turbo noises (even if the boost will go somewhere other than the intake before MS).

I need help brainstorming turbo locations. The engine bay is so tight as is this will be a feat to pull off with a huge turbo.

Potential locations-

-Passenger side somewhere. Best for locating the turbo but I'm racking my brain trying to figure out where to squeeze in the downpipe. Under the engine isn't going to fly with a stock height 4wd xj. I still think this is the best place for the turbo itself. Most of the turbo xjs I've seen online have this setup. Most of those builds are lifted quite a bit, with the exception of that GRM build a few years ago they called the xj-r. That was a 2WD though.

-Over the engine rotsun style. Haven't really though much about this one but I suppose it might work. Not the most polished idea, but you know what they say about polishing a turd...

-Drivers side, right off the manifold. Best for downpipe routing but squeezing intake piping and the turbo in there looks like a nightmare with the steering column and box in the way.

-Remote mount somewhere. This is a cool idea but I haven't thought about it much. Underneath is not going to fly with any offroading or driving through a puddle. I was thinking if I could put it in the cabin somewhere the other day. It strikes me now that maybe it could go in the back portion of the hatch with a xmj style chop top. I've always though those looked cool. Intake plumbing could go outside the body or something. I doubt I'd care after running 7 feet of exhaust tubing.



I'm probably overthinking this. Thoughts?



The new engine build is taking a backseat until I have a more specific idea of what I want for the internals and head. The more I research, the more I realize how critical each component is in relation to everything else. I suspect the engine build plans will change quite a bit as the rest of the project moves along as well.

[LRSimons]

Turbo is going remote control. Mounting it in the "bed" is going to work. I finally feel like I'm making progress!

After doing some searching at work and discovering that lots of people have done a self contained oil system for rear mounted turbos, I laid under there for a while and puzzled out how the plumbing could fit. If you don't care about your floors like I do (and had a conventional exhaust housing on the turbo), routing the exhaust looks almost comically easy. The stock pipe could easily be used with some more tubing and a couple elbows. But noooo, I had to get a twin scroll.

Anyone ever driven a single and twin scroll back to back in a similar setup? Typing that out, that scenario seems far fetched. The twin scroll in theory would help with lag from the extended plumbing needed with the rear mount. However, it's going to be a massive pain to get two downpipes bent out consistently.

Charge pipe looks like it'll go through the cab and passenger side firewall to the engine bay. There's no way a stretch of 3" tubing is fitting underneath. Not exactly elegant, but maybe there's a better way. I haven't thought about it that much.

[SkylinesSuck]

I have driven the same dual scroll turbo with both a divided pulse style manifold and without. There was several hundred rpm worth of spool difference. In a remote mount setup though, I doubt it will matter.