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Turbo sizing, are my manual calculations right?

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Thecarfixerguy

Proven Member
57
20
Dec 13, 2022
Idaho
Before I order parts for my build I'm trying to get well matched parts. So I went down the rabbit hole of calculating my airflow, manifold pressure, and pressure ratio manually. My concern is the pressure ratios seem much higher than the pressure maps I'm seeing for various turbos. I ran calcs for 400HP and 450HP and came up with airflow of 48 Lbs/Min(400HP) and 54 Lbs/min(450HP) with pressure ratios of 3.49 and 3.91 respectively. Am I needing to look at bigger turbos to hit these numbers, and will that kill my spool time?

My goal for the car is a quick spool and fun car to drive around town without hitting felony speeds before the turbo really gets going. I'd be willing to sacrifice a little max HP for a quicker spool.

My thought was if I pick a turbo where 3.5 pressure ratio hits right at the top right of the turbo map I would have the rest of the turbo range for performance at the lower end. Is that a correct assumption?

I attached an image of my homework paper with all the numbers I used for my calcs. Thanks for the help.

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Turbo flow rates and boost pressures are highly setup-dependent, no two cars will be alike. A freer flowing intake tract to the combustion chamber will flow more air, but do so at a lower boost pressure. Intercooler are a major variable to this as well. Exhaust back pressure is equally dependent on manifold design, turbine A/R, exhaust setup, etc. BSFC has so many other variables, including fuel types. It is very difficult to math your way into a solution to this - the closest you’ll come is something like Borg Warner’s Matchbot tool.

The best advice I have is to pick a power goal (you didn’t identify whether it was wheel horsepower or flywheel), pick a turbo fitment style (stock mounting, T3, T4, open or divided housing) and look for similar builds and posts from people who tested the setup that you have in mind. Pick something small to fit your goal that won’t be at the ragged edge of what that turbo is capable of.
 
I made this a few years ago, might help alleviate some of your hand math requirements. You will need excel or open it in OpenOffice/Google sheets. It is just used for rough estimates go but can get you in the ball park.
 

Attachments

  • Motor.xlsx
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Compressor maps will give you an idea of a turbo's potential, but turbine maps will tell you the behavior because response comes from the hot side. Compressor maps are rare enough, though.

But this platform is 30 years old. You're not trying to make a big turbo kit for an engine that just came out or slap some boost onto a riding lawnmower that no one has ever looked at twice before. I appreciate your willingness to look into the numbers/theory, but you can find potentially more useful information here about pretty much any turbos except the absolute newest stuff by either checking what turbos people have used or asking for suggestions based on your goal and mods.

But without further details, I'm going to blindly suggest a Forced Performance HTA68. That SEEMS to fit your second paragraph well enough, but those words are SUPER subjective.
 
Wow, what a complete waste of time

14b for 300WHP
Evo 3 16g for 400WHP
DSM HTA 68 for 500 WHP
FP DSM Red for 600 WHP
FP DSM Black for 700 WHP
FP Zero for 800 WHP
Garrett GT 37R for 900WHP
Garrett GT 42R for 1000-1100WHP
Garrett GT 45R for 1200WHP+
 
Thanks for the input everyone.

It sounds like real world experience beats out math class this time around as often seems to be the case. It was interesting to learn the theory though, worth the time to me.

I was leaning towards 68hta before I went down this rabbit hole, and it looks like that is the plan again.
 
Evo 3 16g for 400WHP

Did you mean crank HP for the evo3 16g? Or are you automatically assuming E85 full beans timing thru the roof?

On my pump gas 16G setup, ecmlink is showing 285 HP at the wheels without correction, and with 0,25% driveline correction it pushes it up to 380 at the crank. I've hit the timing limit on my setup and this is on a healthy 25 psi of boost.

I just cannot realistically see how people could get 400 wheel HP out of this turbo unless they are running insane timing due to E85. I'd say for shitty pump gas and an insanely well put together setup, 400 crank HP would be the absolute max for the E316G.
 
they certainly don’t make that here. The most I have ever made on a non inflated Dyno is 330whp. Back when we had no choice there was a Dyno jet that always gave “great” numbers. That one did 415whp on a 2.3L on e85.
 
Wow, what a complete waste of time

14b for 300WHP
Evo 3 16g for 400WHP
DSM HTA 68 for 500 WHP
FP DSM Red for 600 WHP
FP DSM Black for 700 WHP
FP Zero for 800 WHP
Garrett GT 37R for 900WHP
Garrett GT 42R for 1000-1100WHP
Garrett GT 45R for 1200WHP+

Not at all a waste of time. This platform is old and stuff like the list you have above is well established, no disagreement. But I'm an engineer by trade and enjoy, like many others probably do, diving into the theory, math etc., and watching it line up to the real world. My car is as much a learning tool as it is a vehicle for me to go drive/race. Some people might enjoy learning the WHY and HOW behind the WHAT.
 
Did you mean crank HP for the evo3 16g? Or are you automatically assuming E85 full beans timing thru the roof?

On my pump gas 16G setup, ecmlink is showing 285 HP at the wheels without correction, and with 0,25% driveline correction it pushes it up to 380 at the crank. I've hit the timing limit on my setup and this is on a healthy 25 psi of boost.

I just cannot realistically see how people could get 400 wheel HP out of this turbo unless they are running insane timing due to E85. I'd say for shitty pump gas and an insanely well put together setup, 400 crank HP would be the absolute max for the E316G.
I think that whole chart was supposed to be bhp and not whp. I'd question most of the numbers otherwise.
 
For DSM fitment stuff, the hierarchy is probably closer to this (maximum on an average setup without badly stressing things):

14B for 250WHP
Evo 3 16g for 350WHP
DSM HTA 68 for 400 WHP
FP DSM Green for 450WHP
FP DSM Red for 500 WHP
FP DSM Black for 600 WHP

Numbers go up as you optimize everything, like porting the cylinder head and running E85.

The Garrett G-series is probably the best overall in terms of performance and fitment in single scroll stuff, but that comes at a much higher price.

Again, it all depends on what your goal is, what turbo footprint/fitment you want to work with, and what your budget is.
 
For DSM fitment stuff, the hierarchy is probably closer to this (maximum on an average setup without badly stressing things):

14B for 250WHP
Evo 3 16g for 350WHP
DSM HTA 68 for 400 WHP
FP DSM Green for 450WHP
FP DSM Red for 500 WHP
FP DSM Black for 600 WHP

Numbers go up as you optimize everything, like porting the cylinder head and running E85.

The Garrett G-series is probably the best overall in terms of performance and fitment in single scroll stuff, but that comes at a much higher price.

Again, it all depends on what your goal is, what turbo footprint/fitment you want to work with, and what your budget is.


This all day. I was gonna start asking for dyno sheets of a 68HTA making 500awhp on anything other than an absolute max effort setup, and what the trap speeds of that exact car happened to be. I know Lucas English had some great luck with the OG 68HTA on his Auto 1G, but other than that it's just been heresay. Never any hard numbers. Although the new V3 68HTA I'm curious about. But honestly, $1100+ for a billet 18G-ish turbo is hard to swallow.


Regardless, this is pretty ideal. I would throw Holsets into the mix, but honestly it's so hard to find housings for them now I don't even know if they're worth pursuing. I couldn't even give my HX35 away for $100.
 
All those numbers were whp. If you can't achieve them that's a you problem, don't blame the turbo.

For example 130 mph should be the mark for an hta 68. 400whp won't do that.

The last dyno I did in a dsm in 2001 was a fwd laser small 16g 21 psi turbo blue with an exhaust and afc did 300/300 to the wheels, no cams or fmic and that turbo is 3 sizes smaller than an evo3.....yeah I think I could bump 100whp on top of that.
 
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I don't want to call you a liar, we're better than that over here, but I think we're not being concise enough so these numbers are meaningless without full build specs and at least mentioning what fuel, type of dyno and whether it had correction factors or not. I would love to believe you because that would mean my car is not 285 whp but rather 370whp or thereabout. I would gladly send you my latest log with this result so you can tell me what I'm doing wrong :confused:
 
Send me a log. But the hp estimator on dsm link is a complete lie, it's not even close, don't ever ever use it or even look at it.

I always assume max hp with good fuel/ timing and a turbo operating within its max working range. Over spinning a turbo for air flow doesn't count because it's not reliable.
 
All those numbers were whp. If you can't achieve them that's a you problem, don't blame the turbo.

For example 130 mph should be the mark for an hta 68. 400whp won't do that.

The last dyno I did in a dsm in 2001 was a fwd laser small 16g 21 psi turbo blue with an exhaust and afc did 300/300 to the wheels, no cams or fmic and that turbo is 3 sizes smaller than an evo3.....yeah I think I could bump 100whp on top of that.
This forum really needs to get away from treating records as things that the average user should expect. There is exactly one 68HTA in the dyno compilation thread that makes 500WHP, and it made 501, and his setup was extreme (built, high compression bottom end & ported head from Boostin', big cams). It was also done on a Mustang dyno; on a DynoJet, those numbers would likely be in the mid 400s. That is the only 68HTA car to break 130 MPH that I can find (131 MPH), and the next best is another full build with a gutted interior at 124 MPH. Treat that car as the exception, not the norm. The #2 was also on a Mustang dyno (481WHP), then the rest are 450WHP and down. The highest dyno that wasn't on ethanol was 401WHP, and other dynos go down to 313WHP. If you tell people that they're doing something wrong if they're not making 500WHP and going 130 MPH on a turbo that clearly cannot do it without a generous dyno or extreme setup, you're setting them up for disappointment. Again, on an average setup that most enthusiasts have, 400WHP and 120 MPH trap is a very reasonable goal.
 
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Everything about the above post is 100% incorrect. This is loser talk.

Here is a screen shot of my HTA68 years ago flowing 10lb more a min than FP recommended at 51. Again if you can't achieve the values it's a you problem, not a turbo problem.

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Everything about the above post is 100% incorrect. This is loser talk.

Here is a screen shot of my HTA68 years ago flowing 10lb more a min than FP recommended at 51. Again if you can't achieve the values it's a you problem, not a turbo problem.

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What is more likely - the fact that the 68HTA is not a 500WHP/130MPH turbo for the average user when only one person out of the hundreds sold is known to have done it, or your airflow estimate is off from improper parameters? You have presented nothing reliable - in fact, every time someone argues with you here, I have never seen you present reliable evidence to support your point. It’s odd that you dismiss other logs in this thread about having no validity, yet you happily submit your outlandish data log as gospel just the same. Go dyno that car, show us time slips. Until then, stop polluting the thread with nonsense.
 
Here is a 14b setup I had flowing 35lb/ min
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What is more likely - the fact that the 68HTA is not a 500WHP/130MPH turbo for the average user when only one person out of the hundreds sold is known to have done it, or your airflow estimate is off from improper parameters? You have presented nothing reliable - in fact, every time someone argues with you here, I have never seen you present reliable evidence to support your point. Go dyno that car, show us time slips. Until then, stop polluting the thread with nonsense.

LOl, see guys this is how you win. SHOW some logs make them cry!! This guy doesn't even own a DSM, no car in profile yet he telling the rest of us I am false info who has built 20 different DSM setups in my life. Guys building a DSM is not hard, don't make it as such. Plenty of people have pushed 50lbs/min on a HTA. Just because they didn't run on here to show you a dyno graph doesn't mean it didn't happen. And yeah I am sure my parameters are right, my boost est and real boost match perfectly, but what do I know I only wrote the book on how to tune ECMlink.
 
So where is your dyno proof and 130mph time slips?


This feels like Facebook, and also heavily feels like this clown is trolling just for sake of trolling. Also WTF does politics have to do with any of this?

OP, I’m sure you can clearly see who to trust and who to ignore. Canadian has been around for years and done incredible things with DSMs. Always ignore the guy who wants to talk like an 8 year old COD player. “Lol you got pwned noob! I’m so much better! Mommy bring me my chocolate milk!”
 
This feels like Facebook, and also heavily feels like this clown is trolling just for sake of trolling. Also WTF does politics have to do with any of this?
You're not wrong. This does have a patronizing Fecesbook feel to it. Let's keep the shit talking and attacks to a minimum and keep the discussions civil guys.
This forum really needs to get away from treating records as things that the average user should expect. There is exactly one 68HTA in the dyno compilation thread that makes 500WHP, and it made 501, and his setup was extreme (built, high compression bottom end & ported head from Boostin', big cams).
I don't think letting people know what the potential is based on the highest achievements is bad, so long as it's made known that those results are not common, which has been done in this thread. There have probably been several DSMers who have made over 500WHP on a 68HTA (more than the one listed in the 68HTA thread here on the site), but it should also be acknowledged that those DSMers represent a small percentage of overall 68HTA-powered DSMs, with a discussion about how they were able to get those results - and as Steven pointed out above, at what altitude.

What a lot of people fail to grasp when asking about turbos (those who ask about turbos tend to be a little green, which is why they're asking about turbos and power potential) is what needs to be done to achieve the highest possible results and while maintaining a high level of reliability. It's not easy to get the max HP results, and it takes time, dedication, a will to learn and expand technical knowledge and mechanical abilities, and a good amount of money to throw at the project because shit breaks when you try and push turbos to their limits - more so when you're learning. Most people who ask about turbos and their max HP potential don't usually have all of those, thus, the rest of us try to help them set some realistic initial expectations.

The points you guys are all making are pretty valid. It's just the combative nature of some of the posts and refusal to acknowledge each others' points (some of which are combined with attacks) makes it feel like Fecesbook. There is no need to be a prick when making a point, but after nearly 25 years of moderating forums, I can tell you that some people find joy in it and feel like they're doing everyone in the group a service by putting people in their place. Condescending and pompous attitudes are everywhere. They live more on FB these days because those people tend to like the unmoderated social networks. But we still get some of it here in the forums from time to time.

In any event, the question has been answered with plenty of useful info. I'll go ahead and close this thread, something I haven't had to do in quite a while, since most of the replies that will follow will have little to do with the original author's question.
LOl, see guys this is how you win. SHOW some logs make them cry!!
This is also how you win at driving people away from a community, regardless of how right you might be or how valid your point is. It's one of the reasons why Fecesbook sucks with Q&A. Please make your point without the smug condescension in future posts.
 
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All those numbers were whp. If you can't achieve them that's a you problem, don't blame the turbo.

For example 130 mph should be the mark for an hta 68. 400whp won't do that.
Just popping in to add that I built a TD06SL2 20G nearly a decade ago which trapped 134mph in a 7cm2 housing and made 437whp on English Racing's dyno, tuned by Lucas himself...so 400 to trap 130ish seems totally achievable depending on the car and the driver. I agree that "by the numbers" a 68HTA may be 500whp-capable, and while some have done exactly that there are many more 68HTA users at or below 400 than at or above 500. It takes an extremely-efficient, well-rounded build to extract maximum horsepower from any small-turbo compressor map opposed to screenshots of potentially-uncalibrated airflow logs. The great Curt Brown made 499whp with a 16G almost 15 years ago, but that doesn't make a 16G a 500whp turbo for everyone.


O.P.: Keeping in mind that we're down to just one vendor still producing new DSM turbochargers aside from a handful of guys doing one-off custom work like myself, and given the "450" portion of your power requirement, I'd suggest the DSM Green. The difference between the V2 68HTA and Green is 1.3mm on the compressor inducer and 5mm on the compressor exducer; turbine wheel and housing are the same. The higher trim calculation of the 68HTA compressor makes it a stronger contender at higher pressure ratios, but the lower trim and larger overall size of the 73HTA Green makes it a more well-rounded compressor choice.

If spool is more-important than making 450whp, I'd either try to find a V1 68HTA or possibly get the new 6851S which uses a custom turbine that falls in between the V1's TD05H and V2's TF06. Either of those options will get you to 400ish with better response and recovery than anything else on the market. FP may even be willing to custom-build a Green with the 51S turbine if you ask nicely. If stock-appearance is important, the 73HTA Green compressor with it's 52.6mm inducer can still be cut behind a stock cover...I know a thing or two because I've done a thing or two. :p

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I think where everyone messes up is the intercooler. These 100 dollar huge cores flow like crap, and square endtanks flow like crap, and sharp 90 degree turns off the endtanks flow like crap. Making power is really all about making flow. DVDT Fab was the only one to really figure it out for us.



Here is a 14b setup I had flowing 35lb/ min
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LOl, see guys this is how you win. SHOW some logs make them cry!! This guy doesn't even own a DSM, no car in profile yet he telling the rest of us I am false info who has built 20 different DSM setups in my life. Guys building a DSM is not hard, don't make it as such. Plenty of people have pushed 50lbs/min on a HTA. Just because they didn't run on here to show you a dyno graph doesn't mean it didn't happen. And yeah I am sure my parameters are right, my boost est and real boost match perfectly, but what do I know I only wrote the book on how to tune ECMlink.
Rich words from a log with airflow miscalibrated. AFRatioEST, which is literally the DA table the ECU is 'outputting', doesn't even match your actual output (WB).

And yeah I am sure my parameters are right, my boost est and real boost match perfectly, but what do I know I only wrote the book on how to tune ECMlink
BoostEST is only accurate at peak VE. And your values never match throughout your entire pull anyways.

Our idea of perfectly is different and I'd love to read your book on how to tune link.
 
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I think everything that's been said covers the 'theory' portion, but I'll just throw this out: theory doesn't really tell you much about fun.

My v1 68HTA setup is a lot of fun to drive. It's very simple - the turbo has its stock housings but I got JusMX141 to make me a Mitsubishi/Holset hybrid wastegate actuator (back when he shipped to Canada LOL), with FP cast exhaust manifold, Evo III o2 housing, PTP turbo blanket and a manifold blanket. It's on a crummy self-tune and a Blitz SBC i-D boost controller, but it gets going very quickly and boost control is rock steady at 21 psi to redline with a relatively low duty cycle. You could stretch it out on E85, you could port the turbine housing and o2 housing, and it would make very respectable numbers.

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I honestly think that 400WHP is where things start to go off the rails with these cars. It gets more expensive, things start to break more often, and that early torque is what makes cars fun. When you transition away to higher power, it doesn't necessarily feel as fast or engaging. You're getting a car that's faster when you really get on it, but in a street car, most of your time is spent putting around below 5,000 RPM - not squeezing the car past 7,000. The v1 68HTA is the best of all worlds, really. It matches a stock engine just as well as it matches a built engine with medium-ish cams. It didn't spool any slower than my Evo's 'Big 16G', yet it still feels like it transitions a bit smoother and has more airflow potential up top. It's the ideal bolt-on street turbo, and just happens to be one of the cheapest.
 
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