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over 600hp WITHOUT high (60plus) boost??

4K views 12 replies 6 participants last post by  jlbayes 
#1 ·
Awhile ago I read some article, it might have been on here, linked from here, or totally unrelated to here, where some triple turbocharger setup using ultra lightweight car type turbos with cutting edge fancy 1:1 impeller to turbine weight or something was supposedly putting down something like 1000hp on surprisingly moderate boost. I haven't really heard of it since then.

What i'm curious (both about that and related to that) is what is the biggest power attained without taking boost much beyond 60psi? The reason for this is from reading lots of articles here and elsewhere it seems that streetable O-rings should work up to about 60psi, over that you need not-streetable (short lifespan) fire rings to climb much higher, therefore I had set about 60psi and assumedly about 600hp as the max I should consider attainable on a two stage compound boost setup that I wanted to otherwise have long life. (when I wasn't shortening that with my foot in it)

Since i'm re-going over my build plans and such though recently i'm just reanalyzing my basic assumptions to make sure they are right. My basic priorities again are 1) long engine life (mostly keeping my foot out of it), 2) tow ability (I assume compounds for sure to keep EGT down, max tow HP of 400-500hp), 3) as much power as I can get for an occasionally wild drag time.

#3 could include nitrous, propane, CNG, super cool oversized intercoolers - just curious whats possible and feasible without the extreme pressures that it seems fire rings are required for which seemingly put a limit on boost pressure.
 
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#2 ·
boost really isn't an indicator of power, cfm or lb/min is what tells you how much air the compressor is compressing.

One turbo, say a hx50, may push over 1000 cfm at only 30 psi of boost

While another turbo, say a hx35, might only push 650 cfm at 30 psi of boost.


Boost is really just a measurement of restriction, it really does not = how much air is being pushed. Measure boost is a valid way to compare two identical turbos, but not 2 different turbos.


I am going to just take a random guess and say you will need 1200+ cfm worth of air to push 600 hp, but it is late and my mind is not all there right now.
 
#4 · (Edited)
boost really isn't an indicator of power, cfm or lb/min is what tells you how much air the compressor is compressing.

Boost is really just a measurement of restriction, it really does not = how much air is being pushed.

I am going to just take a random guess and say you will need 1200+ cfm worth of air to push 600 hp, but it is late and my mind is not all there right now.
I am aware of that in theory but I cant get 2000cfm at 1psi either. I've been trying to read and use the search function and similar looking at others builds, and it seems pretty much a given that around 600hp tends to involve around 60psi to reliably hit.

The only reason this is important to me is that 60psi seems to be the limit of O-rings which are compatible with an otherwise long-lived engine (hundreds of thousands of miles if not tromping it) in a way that fire rings are not.

Therefore I am curious about builds with O-rings (therefore maxing at 60psi) in say the 600+ HP range and what they might be doing differently since it seems uncommon. :)

I know propane, methanol, and nitrous can add power - the first two extra fuel require more air hitting the same problem. Nitrous i'm not sure about but I assume more air in the cylinder still = more pressure. If my ultimate limit for RELIABLE hp is cylinder pressure i'd rather just make it with the big turbos i'm paying for anyways. (if 600hp turbo = 600hp spray no reason to spray) But if it's easier on the engine I want to hear more.


I think if you're going with a single, 600hp and under 60 PSI is possible with the right supporting mods, but it won't be very streetable... twins would probably do with without much sweat, but have their own peculiarities
Definately would be twins at this level even if just for towing EGT's. The towing is higher priority than the dragstrip power which is just for fun. I'm just seeing how far I can push dragstrip fun in theory without going to fire rings/exceeding 60psi where they are apparently needed.

I am aware that bigger and bigger injectors become more of an issue as power rises - but i'm not averse to swapping in different sets of injectors either. I just don't want to touch the internals or turbo design again - I can overdesign the turbo a little bit and then only change injector size instead of altering the whole build. Hence my exclusive focus on the moment is the turbo.

If you meant driveability quirks beyond big injectors over 600hp or specific to compounds though please comment more though i'm here to learn.
 
#3 ·
I think if you're going with a single, 600hp and under 60 PSI is possible with the right supporting mods, but it won't be very streetable... twins would probably do with without much sweat, but have their own peculiarities
 
#5 ·
For one, I don't think you can get 600 hp without at least 4k governor springs, probably 5k.. and they get real touchy on the throttle in a hurry.. Also, when choosing delivery valves, etc, what's best for the track/dyno may absolutely be horrid to tow with..

Then there's the rest of the drivetrain.. tranny and rearend that aren't going to like 600 hp with a 20,000 lb load for extended times either.
 
#8 ·
Kinda jumping ahead, I prefer to focus on one part of the problem at a time..

Already planned 4000rpm, though i'm not sure how you get to 5k with that destructive vibration I hear happens around 4200-4300 plus thought direct injected didn't like to wind to 5k ever..

If I take it as far as 600hp I was seriously considering the FSO-8406 tranny swap, despite others saying even the NV4500 should take that with a stout clutch. Rearend I assumed should hold up - the power is mostly for tromping on it in fourth (since even third would spin the tires i'd assume) for an unreal highway pull.

Nobody tows with 600hp constantly - you dial it down in 'tow mode' even if it's just keeping your foot out of it. (or the 600hp figure is on propane, methanol, nitrous, etc)


I'm told others tow successfully choosing injectors for around 400-500hp tow loads (which is probably also about the max feasible cooling load) and was wanting to make up the difference from there to the power goal with a mix of nitrous (if needed) and added nondiesel fuel of some sort like propane/methanol to avoid how stumbly fuel-only injectors get much above that.
 
#6 ·
I made 473hp uncorrected on 42 psi from a 351CW last fall. I haven't dyno'd my new turbo (50 psi) yet, but I'm expecting it to support 550 if I give it the fuel. If that same power-to-boost ratio can be maintained to 60 psi, you would have 660hp. I don't know how realistic that is since there are a lot of elements that affect power production.

I'm not sure where you're hearing that 60 psi is a hard and fast "limit" of o-rings. While reliability is always going to fall off with increased cylinder pressure (not necessarily boost), many people that run them are pushing o-rings to 80 and beyond and a lot of those trucks are daily drivers. Hell, I'm running 50 psi and 20 degrees of timing on a 310k mile head gasket with recently torqued socket head bolts. Will was running 80 psi and 26 degrees of timing when he finally popped his original head gasket on the junker drag truck, and he was using used stock bolts. He cut his own o-rings into the block and (last I checked) was running 90 psi and over 30 degrees of timing. He's had a bit of a hard time keeping head gaskets in it lately after putting a Hamilton head on (dropped boost from 90 to 75 psi) and bumping the timing up to 38 degrees. Timing has a huge impact on cylinder pressure. I bet his setup would be street-reliable if timing was backed off to the low 20s, which is about the max you'd want for towing anyway. Fire rings have also come a long way since they earned a reputation of not holding up to heat cycles. Non-fuel power adders (water injection, nitrous) increase cylinder pressure and will do more harm than good if reliability is a concern.

Airflow is the key to supporting power. There are two ways to get airflow. Increased air mass (more boost or cooler charge air), or more RPM. You could build an engine that would make 600hp below 60 psi. To do that, you'd have to be turning well over 4k, which would require building the engine to breathe well at those speeds. Big cam, big valves, severely hogged out head, giant turbine housing on your secondary, high timing. Such an engine would be a real turd on the street, and especially while towing. If you want an engine to tow well, a fast spool at low rpm is the thing to focus on.

You don't need to be concerned with o-ring reliability, especially if you're spending most of your time at or below 500 hp. I'm guessing I'm pretty close to 500hp right now, and even when I was back in the mid-400 range, I was never asking more than about 1/3 to 1/2 throttle to accelerate up to highway speeds at a "normal" rate. It's hard to make the argument that I wasn't driving like a jackwagon if I was using any more throttle than that. Passing semis on the interstate at speeds of up to 80mph with my 24' 5th wheel, I wasn't seeing more than 32 psi on the 351CW I had at the time. With this 62 FMW, the same blockhead move has me closer to 27 psi.

Not trying to bust balls or anything, but boost is only a small part of the equation when determining how to build the engine to your needs.
 
#9 · (Edited)
I'm not sure where you're hearing that 60 psi is a hard and fast "limit" of o-rings.

While reliability is always going to fall off with increased cylinder pressure (not necessarily boost), many people that run

Non-fuel power adders (water injection, nitrous) increase cylinder pressure and will do more harm than good if reliability is a concern.

Not trying to bust balls or anything, but boost is only a small part of the equation when determining how to build the engine to your needs.
Thanks for the specifics... well the hearing 60psi was just based on reading older commentary and using the search function. :^) Since if I ask questions everyone will tell me to do that first anyways. It just sounded like 60 to 70 was where people started going to fire rings because pressure was too much to last but those might have been 8 year old postings too. The impression I got taking notes from others is that 60psi should be on the top end of the conservative side of "this engine should still last a long time" if that's a better way to put it. I want more than 'street reliability' I want "can drive this 2000 miles away from home and tromp it a few times without having any fear of blowing up, still reliably getting back". If even 600hp in temporary jaunts is too much for that I may reevaluate.

In terms of cylinder pressure vs power, if I could get the power on just turbo boost and fuel i'd happily do so. In gas engine circles some suggest nitrous may be easier on the engine than turbos - I don't know if it's true there, or here though. I don't actually need less than 60psi - i'm content building a compound system for 60psi as it is, it just sounds like over becomes increasing risk. Turning 4000rpm is already expected, beyond not desirable or planned. Wanting a turbo to come on low is one reason for the compounds - plus cool towing EGT at 75mph even uphill in the mountains and no smoke ever. But I was still curious about that truck I first mentioned supposedly putting down insane power on like 20-30psi and wondered if it was lies and BS or part of a new philosophy of building. I can't find newer mentions of it really.


My priorities are simple:
1) Longevity. I would like this to "last as long as stock" minus putting my foot into it. I'm aware if I run it hard it will take life out of it each time - that's fine and until I have a spare built and ready to swap in I wont lay on it too often - but if I run it easy (like I do most of my vehicles most of the time) it could go a few hundred k-miles. My understanding is O-rings are zero compromise on longevity but fire rings cant last as long even if they are better now than in the past, so my goal was to just use O-rings as a sensible and not too expensive upgrade.

2) Towing. Even if I could have 900hp in a daily driver if it doesn't want to tow nicely then thats "too far". I'm pretty sure i'll hit the limit of injector driveability on a 12v before long anyways - already planned to size for around 400-500hp fuel only which sounds like it should still be driveable, still tow okay, and only a little MPG penalty. I think i'd like compound turbos just so I can legitimately tow with my foot in it keeping EGT's down even if others have done singles at 500hp. The compounds also make the 600-mark easier, i've seen singles run big power but not without high EGT's at lower rpm and this MUST tow well because it's going to spend probably 85-90% of it's life with a load behind it varying from 3-14k.

3) The 4th Gear Pull. Renamed from as much drag HP as I can get because what I really want is to just be a monster when it comes to on-highway acceleration with or without a load. If I go the FSO 8406 it wont be speed shifting anyways/i'll lose quarter mile accel from that alone but tow trumps perf esp being sure it doesn't break down 2000 miles from home because I had to tromp a Mustang in the other lane. I would love to be able to break into the 11's for acceleration rate (even if slower shifting wouldn't make it feasible) having had a ride in an 11 second truck once. I thought this might be possible with 600-800hp and the right design (ie 400-500hp injectors with separate nondiesel fuel added) shouldn't kill towing or streetability or longevity. Pretty sure all those things are killed over 800hp.


If I fail in goal #3 I can always dial back my expectations a bit because it's the most expendable part of the equation, but I was under the impression based on others builds that it shouldn't be all that big of a deal especially if nitrous and propane/methanol are on the table as options. Not because I need them for the power, but because they let me size the injectors and optionally turbos to be more streetable than otherwise. Any advice from people is appreciated.
 
#7 ·
Like has been said, boost is not the determining factor on how much O-rings will hold. It's mostly cylinder pressure and when it happens, with heat playing somewhat of a role too. Timing is probably the biggest single factor leading to head gasket failures.

As an example of why the term "boost" is misleading. I can adjust the waste-gate on my secondary so that my primary is only making 25 psi with a total boost of ~80 psi or, I can adjust it to where the primary is making 42 psi while the total boost still ~80psi. Now since my total air mass is limited to what the primary is pushing, you can see that I'm pushing much more air in the second case than the first case at the same "boost" level. And, it will make quite a bit more power too.

As far as how much O-rings will hold... I haven't had an engine that was producing less than 80 psi of boost in many years. Sometimes, it's been closer to 100 psi. Never had a problem with O-rings unless I pushed the timing over 30. And that was with engines up to the low 800hp range. With the new engine the story is a little different. One pass with just over 80 psi, and I blew the head gasket in five different places. Same "boost" level, but much larger air mass and hp =
:kaboom:

As far as hp and boost goes... I can slide my plate back to where it only makes low 60s boost, and it still makes over 700hp. I'm thinking I could probably loosen up the waste-gate on my secondary and let the primary do as much work as possible and make still make well over 600hp with less than 50psi of boost.

To the OP, what you are looking for is somewhat of a standard popular build. Turbos would be a 351/s475 or similar combo, benched pump with 4 GSK and 90-100cc DVs, 5x16 injectors, O-ring and port the head while it's off. Run a plate and 18 degrees of timing for towing, pull the plate and bump the timing to 26 or so for racing. That build will tow well, and probably run high 11s.
 
#10 ·
Like has been said, boost is not the determining factor on how much O-rings will hold. It's mostly cylinder pressure and when it happens, with heat playing somewhat of a role too. Timing is probably the biggest single factor leading to head gasket failures.
In theory I understand that, but what i'm really trying to find is who if anyone is legitimately making 600-800hp on less than 60psi to see if they have any unique build secrets because it sounds uncommon. :p



As far as how much O-rings will hold... I haven't had an engine that was producing less than 80 psi of boost in many years. Sometimes, it's been closer to 100 psi. Never had a problem with O-rings unless I pushed the timing over 30. And that was with engines up to the low 800hp range. With the new engine the story is a little different. One pass with just over 80 psi, and I blew the head gasket in five different places.
Well good then my goals of 600hp and 60psi should be conservative enough to last me 500,000 miles. :^)

Or not, but i'm being a little more conservative in absolute max goal. This isn't daily driver reliability I need, but "2000 miles from home away from the shop" reliability because this is the truck that i'll be picking up things cross country and then towing back home with constantly. Even 600/60 may be too much with that in mind - if so please tell me now.

I dont NEED the power I would LIKE the power, plus it seems within range if I was considering compounds anyways. But if i'm likely to lunch an engine at 250,000 miles in tromping an uppity Mustang (after a life of not tromping on it all that often at all, I wont be hitting dragstrips or anything I just like power reserve to get out of trouble - ie semi truck merging on highway, doesn't see you and your 14k load, so it's slam the brakes or use the throttle) then yes I better change my assumptions. (not that i'm saying the engine might not be worn out by 250k miles anyways, but there's a difference between "needing an overhaul" and "you blew it up when you hit the throttle", I want to replace it when its worn out not because it exploded)


To the OP, what you are looking for is somewhat of a standard popular build. Turbos would be a 351/s475 or similar combo, benched pump with 4 GSK and 90-100cc DVs, 5x16 injectors, O-ring and port the head while it's off. Run a plate and 18 degrees of timing for towing, pull the plate and bump the timing to 26 or so for racing. That build will tow well, and probably run high 11s.
And yes, everything you said is everything that i've read seems to be "not unreasonable to expect". My bigger curiosities is "how driveable is that build under all conditions towing and not towing" and is the engine likely to blow up before it just wears out at that power level? I'm curious at what power the catastrophic explosions start happening so I can stay well below that level. I'm wondering if my plan for nitrous/nondiesel added fuel (so that normally smaller injectors or even turbos can be run) is even necessary or beneficial. Or alternately if doing so could goose the power a little further - without killing everything still.

I'd love to hear from someone with exactly that build (sounds similar to your own?) about how the driveability and manners differ from stock under part throttle conditions.

What is a 'plate' though that's new to me?
 
#11 ·
I guess the old saying is holding true.. "timing is everything" lol
I completely agree that it's cylinder pressures that matter (peak pressure at that), not manifold pressure.. though the two are related to an extent.

Another thing I'd consider for that kind of power is a cam upgrade.. less parasitic pumping losses, less manifold pressure = higher turbo efficiency = lower intake temps and EGTs

I have *heard* of the 351 putting down 600 hp, though I think that's really pushing the limits on it and associated components... I'll let you know how that goes when I dyno my truck (probably fall time).. My goal is a stout 500
 
#13 ·
5ks are a bit misleading. Most trucks do not/will not make power up there. There is the potential to turn that amount of rpm however the gov springs can be set up to limit fueling to 4k rpm. I have 5ks and do not turn the engine more than 4k rpm. No need to do so with my setup.
 
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