364.5 vs 366 SXE for my truck?

freddie · Jan 10, 2020

I've read and reread all of the SXE threads to the point I'm dizzy. Thought I'd just post it and see what everyone's thoughts are.

230/100 injectors, all of the associated mods.
E4OD
4.10 gears (I have 3.55 but plan to make the swap this year to 4.10s)
35" tires
Will try tunes from a couple different tuners

Priority is moderate to heavy tow performance. Really want this truck to tow great. We have a lot of 55mph roads with hills, I envision a truck that does not break a sweat, minimal downshifting, etc. Not going to have it on the track or anything, but I'm sure I'll spool it up for grins.

I think I have it narrowed down to the 364.5/.91 and 366/.91 based on everyone's feedback on here..

If I was sticking with the 3.55 gears I think the 364.5 would be the way to go, but once I install the 4.10s, would I wish I had the 366?

Let's hear it?

Zeb · Jan 10, 2020

364.5/73/.91 You’ll be 2,200-2,400 rpm in direct at 55-60 mph and 35” tires. The 364.5 will be rocking at those rpm.

366 would work quite well at those rpm, but will spool a touch slower on take off, etc.

JCart · Jan 10, 2020

If it was me I’d do 364.5/.91 A/R exhaust housing for quicker spool, will be better for towing in hilly terrain. 3:55 gears will work, pending how heavy you tow and would work good with 364.5 too. I’d want the quicker spool with the auto tranny too, such a pain in the arse to try towing when under the turbo... resulting in Smokey hot EGTs. In respect to tunes, recommend Jelibuilt, been really happy with mine so far and Brian has been quick to respond to questions.
j

chaselee · Jan 10, 2020

I'm running the 364.5, 205/80 full force injectors, 37s and 4.10s. truck runs great and spools fast.

psduser1 · Jan 10, 2020

Zeb said:
364.5/73/.91 You’ll be 2,200-2,400 rpm in direct at 55-60 mph and 35” tires. The 364.5 will be rocking at those rpm.

366 would work quite well at those rpm, but will spool a touch slower on take off, etc.

Devils advocate-once you're moving, the 366 will be your friend when you get to a hill, in direct, and pushing 28-3000 rpms.
Itll depend on driving style and conditions.

You have plenty of fuel available, the only limit would be how often you tweak the tunes.
If you are spending more time midrange and up, i.e. going down the road, the 366 would be the better bet. Lots of time stoplight to stoplight, the 364 would be less headache, trade off being a limited top end.
How much load will you be seeing? Empty truck, diving around, or hooked to a 5ver with 8-10k+ chasing you?
It does make a difference.

freddie · Jan 10, 2020

All great points so far, thank you all.

I plan to haul my buddy's truck to some events on a gooseneck, around 13-15k. Not every weekend but yeah.

Driving is mixed I guess. I'm just torn. Lol. Probably can't go wrong with either I guess?

Back woods · Jan 10, 2020

cjfarm111 · Jan 11, 2020

No personal experience with those size but I would think the 366 would be fine. I like my 364.5 but I’m only running 180/80’s. Must likely though a tow tune with your injectors will be fine with the 364.5 and it will spool a little faster. Unless you plan on racing or running a hot tune all the time I would stick with the 364.5.

Back woods · Jan 11, 2020

The 366/.91 does spool really well. I run one on my truck with stock split shots. It makes 20psi @ 2000rpm. If you are towing at 1700rpm it can be lazy but starts coming alive at 1800rpm. Gives you some room to mess around with tuning as well.

TMCCOY · Jan 11, 2020

I've run both on my truck with my 175/80's and towed a lot with them. With the large turbine version of the 364.5 and .91, both turbo's spool very similar from stand still. The 364 *MIGHT* be a little quicker. Once under boost, the 364.5 is much more responsive to throttle input. Daily driving, the 364.5 is better but it feels like a smaller turbo as it is. It doesn't have the mid and top end the 366 has. Towing, I think the 366 was better because it is constantly spooled and is great. No difference in EGT's I observed.

In my case, I moved to a high elevation (5,000) and going to the 364.5 was helpful, but I'm also dealing with crappy nozzles on my PIS injectors and emissions now so getting more response was something I thought would be good in combination with the high altitude.

Just depends where you want the benefit most.

freddie · Jan 13, 2020

I guess I'm leaning towards ordering a 364.5 unless someone comes in with new info. Would love to see a dyno comparison between the 2.

JCart · Jan 14, 2020

freddie said:
I guess I'm leaning towards ordering a 364.5 unless someone comes in with new info. Would love to see a dyno comparison between the 2.

I’d call the guys at KC turbos they should have comparative data I’m thinking. Thought there was a post on here about both turbos on same truck for dyno data and real world towing anecdotal info. Will be interested in what you experience Freddie, keep us posted. For now I’ve just rebuilt my stoker with KC internals (their exhaust wheel, shaft 360 bearing kit and 1.0 A/R) and think it was a billet 6x6 intake wheel from Clay at RiffRaff. With newly installed FFD205/30s and Jelibuilt files spools up quick, will be interesting to see how long it can take it. I’m guessing I’ll be chewing on similar issue so will be good to know how you make out.
Cheers,
j

freddie · Jan 15, 2020

Thank you for the input. I called and talked it over with Irate also, and they too suggested the 364.5 so I ordered one.

Strokersace · Jan 15, 2020

freddie said:
Thank you for the input. I called and talked it over with Irate also, and they too suggested the 364.5 so I ordered one.

Did you get the big one or little one?

freddie · Jan 15, 2020

I got the 364.5/74/.91

TMCCOY · Jan 15, 2020

The 364.5 is a great turbo for most normal uses. FWIW, the little one is more responsive and drives great with small injectors.

INFRNL · Mar 29, 2020

any updates? What are your thoughts?

I was running a 369 SXE with my 250/100s which was recommended by 1023 but Matt at Irate recommended the 366 SXE since I live around 6500' in elevation and can get to 9000+ in short time. I got TMCCOY's 366 SXE (Thanks again).

The 369 is fun but laggy and i don't like it for towing with my 35's and 410's. I have found ways to still get off the line ok without the lag but I feel that I should be able to punch it and have very minimal lag (not going to happen with these turbos/my setup)

I just installed the 366 the other day so i will have to get some time before I can make any decisions. I can say it spools a tiny bit faster and seems more responsive from 55/60 mph up as well during normal driving. I probably won't be able to tow with it for a little while.

From what I've been reading, It seems like the 364.5 is an excellent turbo and I want to pick one up to try as well. Playing with these turbos will also help in my decision of what to use in my 76 project that has a zf6 rather than auto.

anyway, hope you are liking the turbo. I think you made a good decision for your use

freddie · Jul 29, 2020

Thought I'd follow up with an update.

SDK Tunes (have not asked for any revisions YET)
I still have 3.55 gears with 35s.
I have checked for boost leaks and feel confident that there are none - there were some originally but I have found and fixed them. Even checked with soapy water and I can't find any bubbles.
I did find that my driver's manifold/up-pipe connection leaked, it had soot showing a leak, so I snugged that up.

Truck is a blast to drive IF the turbo is lit. It seems really easy to get under the turbo though, and even unloaded in overdrive at 50-55mph, ~1400 RPMS, it just doesn't seem to hold any boost unless you are manipulating the throttle to build some. Pulling a 5k trailer through some rolling 55-60mph hills, I had to shift out of OD to keep from smoking, just because the turbo would not stay lit. It was right on the edge of lighting the turbo or getting smoky, and I end up driving watching the passenger mirror for smoke. I want/expected a lot better driveability than that.

If you roll into it to get the turbo lit or downshift, it does spool extremely quickly to build boost.

At this point I really want to regear. I was set on 4.10s, but I am also contemplating a change in tire size. Wife and I want to buy a truck camper and tow decent size fiberglass boat - for stability sake I think it is best to drop down a few tire sizes and run a tire with higher rating too.

Anyways, if I stay with 35" tires, I think 4.10s would be perfect. But if I drop to a 33", not sure whether to go with 3.73 or 4.10 gears, and I'm curious what everyone's thoughts are. I already have the 4.10 gear sets for the change, but would need to buy 3.73 gearsets if going that route.

I am leaning towards 4.10 gears unless someone is going to talk me out of it. I added an attachment that shows some RPM calculations based on different gear ratios and tire sizes.

Strokersace · Jul 29, 2020

I personally have had the 35’s and 4.10s as well as the 33’s and 3.73s. They run within about 50 rpm of one another and imho it’s the best dd/towing setup for a 7.3 auto. At cruising speeds (70 mph), you’re into the power curve at that point and not under it. But not too much into it that mileage suffers empty. But far enough Into it that if you ask it for more when towing, you’ll get a response immediately.

It comes down to what you want for looks/height and use. Either is a great combo.

JCart · Jul 29, 2020

Truck is a blast to drive IF the turbo is lit. It seems really easy to get under the turbo though, and even unloaded in overdrive at 50-55mph, ~1400 RPMS, it just doesn't seem to hold any boost unless you are manipulating the throttle to build some. Pulling a 5k trailer through some rolling 55-60mph hills, I had to shift out of OD to keep from smoking, just because the turbo would not stay lit. It was right on the edge of lighting the turbo or getting smoky, and I end up driving watching the passenger mirror for smoke. I want/expected a lot better driveability than that.

Sounds just like my 97 CCSB 4x4 with 3:55s (35” tires) and Auto tranny.... under the turbo... (stock turbo mind you). Went to 1.0 exhaust side and can think the .91 would be even better. Felt like I was either on the fuel for boost... on the brakes or coasting with the auto. Swapped to ZF-5, so much nicer. Current truck in sig is nicer 4:10s 37” tires with ZF. FFD 205/30s and Jelibuilt tunes sparked it right up. Thinking 364.5 with .91 would be beauties... for what I do.

Thanks for up dates fellas.. cheers stay safe.