ok. Just did the manual calculations again.

Using BSFC= 0.65, 800HP target, 6500RPM, 91%VE 150F intake temp 12:1 AFR and 408ci. im getting Total air flow of 104lb/min. Im assuming this is halved for twin turbo. I then am calculating a required MAP of 33.63psi (absolute) which is 18.93 psi boost. Again, this seems excessive??
Im get a Compressor discharge press of 35.63 by assuming 2 psi loss in plumbing. Compressor inlet press is 14.7-1= 13.7 psi. These give me a pressure ratio of 2.6?

Whats the deal? even with the calculator in the previous post with http://www.squirrelpf.com/turbocalc/index.php link it is telling me similar things....?

why is such a high boost needed?

Are my initial values of BSFC, VE, AFR..ect incorrect????

 

throbbinV8- Can i ask if you would explain to me where or how i am going wrong with my calculations?

Thank you,

peter

 

Hope the pair hold up on my Mopar 408ci smallblock....knockoff replacement gt42.....75mm/102mm compressor, 75mm/82mm turbine 1.05ar....499$ each
Figure a couple million gt42 to be replaced every so often has to be a lucrative endeavor...I bet quite a few of these turbos get used on big trucks.
#ad


#ad



finally getting them packaged...all piping is done but no decent pics
#ad



Thing I got enough bolts on the center ports?
#ad

 

^^ holy shit!

 

How about a slightly more casual approach? Personally I didn't do all the calculations you've done as I've always thought there are so many variables from engine to engine and you can never be sure of volumetric efficiencies (etc) unless you have tested them. If you were building an all out competitive race car then the calculations are probably worthwhile - for a fun street car... probably not.

If you want around 800bhp (at the flywheel) then you need to push around 80lbs of air per minute. If you're running twins then you need 40lbs per minute x2.
Next decide roughly how much boost you are comfortable running through your motor. If its 14.7psi then you're looking at a PR of 2 etc. The PR formula is simple; (14.7+chosen boost)/14.7 = PR. Dont worry about pressure losses just keep it simple. Choose your PR (according to the boost you're COMFORTABLE with) before the next step.

Get hold of some compressor maps and look along the line of your chosen PR. Ideally you want the centre island to encompass 40lbs per min of air at that level. If you're slightly out of the centre island that turbo may still be workable, although slightly less efficient than it could be. It really doesn't need to be any more complex than that. When you've found something you think may be suitable then post it up and some of the experienced guys can advise you on AR or trim.

A little (non-patronising) advice from an older guy who has also been your age (LOL). Dont worry too much about chasing 800bhp. Its far more important to build a street car thats reliable and fun to drive. A genuine 500bhp car can be a handful on the street but can be plenty of fun too. When you start going over that, putting power down and keeping the thing in a straight line gets progressively more difficult and expensive. Theres really no point in building something un-drivable just so you can say it makes 800bhp on a dyno. You're genuinely better off erring on the conservative side with power if you want reliability and fun. A wide power band with good low end torque is way better than all out top end horsepower. Hope this helps and saves you ball ache in the future.

 

I always wondered about the variables and stressed about them as they are only estimates. But the range of the estimate does not affect the result all that much. Saying that, I understand the term 'keep it simple'.
As for boost. Ok so I work around the boost I want to create. I was expecting to make about 10-12lbs. So that makes my PR 1.7-1.8. Which brings me back to choose from more realistic turbo's.
As for 800hp- I was told Ill squeeze this in EASY. I know its alot but i can admit im an extremist. So taking my stock block to the limits is what i want to do unfortunately. I guess i cant relate to having too much power as i havent been there yet. But no doubt i will learn after this build. Also my driving technique involves me steering with my right foot and if the car is not doing what it wants then i just stomp down on it harder until i re-gain control so there may not be as much regret as any other normal person. Yes it is in a street car but later on i think i want to put this engine into a light coupe and pull some impressive 1/4 mile times. My CR is not too low at 9.2:1 so is it true that my car will have a decent pwoer range? My freinds are saying my car will haull ass even with out turbo's...

 

I have a set of 66mm borgwarner that would be a good fit. I was going to run them on my 410w but may go a little bigger. Was planning on 1000hp. They have a larger 72mm turbine, which is a good fit for the larger engines. PM if you'd like any more info.

Throbbin, are the wheels balanced at all ? i don't see any grinding.

 

Personally I'd look in the range of 12-18psi for a decent street car (possibly approaching the edge of streetability). So check out compressor maps along the 1.8PR to 2.2PR lines. If the PR simply wont give you 80lbs/min (or 40lbs for twins) then your expectations are a little high for the 'boost risk' you're willing to run. Also be aware that the more power a turbo gives at a given PR, it generally follows that the compromise will be spool characteristics. Even going for smaller AR's doesn't work as it chokes top end with exhaust back pressure. Theres no getting away from compromise with turbos - thats just the way they are. If you want fun on the street you need a 'reasonable spool'. Living with 4000rpm of lag just to have 800bhp at 6500rpm (in my opinion) simply isn't worth it.

If you can get a compressor map thats healthy in the 1.8PR to 2.2PR range then it'll give you space to grow power-wise by simply cranking up the boost from a start point of 12psi to 18psi assuming your tune is ok and there's no detonation. You'd probably need decent fuel, intercooling and maybe some water/meth injection to keep 18psi in check with a 9.2:1CR. Of course all engines are different so you'd just have to test incrementially.

You already have decent cubic capacity so you simply dont need the boost or rpm a 302ci (or similar) would need for similar performance. I absolutely guarantee that with even 12psi in a central efficency island you'll have enough torque and power to gain a healthy FEAR of your car. Thats not the same thing as respect... it means you probably wont drive it as often or as hard as you thought you would LOL. You'll see...

 

Looking at some maps The T04E 60 trim is right in between the island and the choke line. From what I can see it will be ok but there is not much room to grow... Also arount the max efficiency region. And turbo speed is acceptable.

Looking at a GT35R 76mm 52 trim seems similar to the T04E 60-1.

The GT35R 68mm 56 trim so close to the centre island.

Which out of these would be more desirable? I can get two t04E 60-1's for a good price. all 100% Garrett internals with 6 months warranty.And the guy is tellin me these are proven to be populat on big inch v8's?

10secgoal- Im more after garrett's. But thanks anyway!

 

Not vsr balanced though the turbine wheel is balanced and compressor wheel is balanced on the back...I believe vsr is used mostly on aftermarket turbos.
O

 

No sweat. Try excessive motorsports if you pass on those. He's a garrett dealer.

 

is ne a member here?

Thanks

 

I'll have to pass on advising you on Garretts - I've only run Holset and Master Power to date. I'm sure a Garrett veteran will be able to help you decide.

 

hey guys im new here, well not new been lurking in the shadows for a long time, anyways EBOOST all your calculations are correct enough for what your doing with the exception of one....... your BSFC is insainly high and thats throwing you WAY off the mark. go into the squirrel performance turbo calculator like you already did and change your bsfc to a reasonable .52 or so and all of a sudden your engine is way more efficient than you were giving it credit for (actually that should be pretty accurate number for your engine and all the calculations come out saying that to hit 800 hp with your setup around 18 psi boost will do the job. you will have a max airflow of about 91 lb per min. with twins that should put you in the middle of the map on a t61 or equivalent, but as a side note stay away from the t04 60-1 turbo as it is horribly inefficent and old design. just compair the maps side by side of the 60-1 and t61 or s300 borg turbo to see how bad it is .. best of luck skunk

 

thanks skunk. Welcome to the turboforums!

I appreciate you taking the time to check my calculations. Firstly i was under the impression that BSFC of a NA car is 0.5, boosted application BSFC was between 0.6-07? I have never heard of 0.52 for turbo? Is seems a little close to NA's value???
Secondly, i DO trust the calculations, but as throbbin v8 has pointed out which i agree with is that 18 lbs of boost in a V8 for a measly 800hp is way too excessive. The engine NA would be capable of +600HP. So the use of such a high boost to get another 200HP concerns me. To me, a boost pressure of even 15lbs will be able to push me over the 4 figure power level.

Please let me know what you think of my opinion.

Thanks

 

As retarded as it may be, the exact T3 turbos Car craft used will make 800 fwhp without a problem. I personally have never killed one of those turbos and they make a GREAT turbo for a low budget street oriented setup. Would i use them on a serious setup? Probably not.
2 of those 57mm turbos made 640 whp on a completely STOCK worn out, stock factory cam 402 bbc thru a manual transmission on a local guys car and they never blew. Another local guy had em on an unknown 350 sbc in a 56 chevy sedan delivery and ran a 10.78 in the 1/4 mile. The things are retarded fun and the failure rate so far has been zero. My stock 3800 in my 98 camaro has one and runs mid 12's at 15 lbs boost. 10k miles of street use so far and no failure.

I aint saying use em for your build but they sure are a lot of fun!

 

https://www.theturboforums.com/smf/index.php?topic=114808.0

Heres the link to the 402 and ebay twins. At the very least its worth a good laugh to read it.

 

i had two chineese turbos and sold them already. I plan on using reputable brand ones for my engine. I have been advised not to skimp on turbos as they could kill my fresh engine. So i have bugeted $1600 and can get two to4e 60-1's with 100% garrett internals and 6 months warranty for my budgeted price. I sold my t3/t4 cheapy's for $600 which was good considering i paid $900 for the two with manifolds and shipping from USA.

So basically im not interested in any luck with cheap turbos. Also not keen on any MP turbos or turbonetics. Pretty much set on garretts.

Thanks tho.

 

ok eboost i can answer your stuff in a second.. trbo355 man you are my hero, haha i have been reading what you did with the worn out junk yard 2 bolt 350 i have made it through about 24 of the 156 pages on that thread, needless to say i was amazed at the level of performance that crap hole was able to withstand. very cool and very good work. ok now eboost your perseptions on bsfc may be a fair bit off. first of all you talk about making 600+ horsepower from a small block and then need 18 pounds of boost to get 200 more hp. well there are a few things that the 600 horse engine has going for it that wouldn't lend itself to turbocharging, first of all the ability to make that kind of power will require a static compression ratio in the 12:1 or so area which makes the engine extraordinariliy efficent but you CAN NOT run boost with that much static compression becuase then the dynamic compression would be so high the motor would detonate itself to death in short order. another thing required to make that power on that dispacement is a very radical cam with a lot of duration and substantial overlap, which again can not work with a turbo because the air fuel charge is going to come in the intake valve and right out the exhaust valve during overlap which will due two things... one it will make crap power but the raw fuel in the exhaust will raise your egt so high that you will insinerate your turbine blades. another thing is that 600 horse race engine probably has a bsfc in the neighborhood of .42 because it is super efficeint with a combinations of the intake exhaust and valve timing tuning. there is more but i just realized i was just rambling on so i will leave it at that but if you do want to know more i can explain more. also check out this http://www.squirrelpf.com/turbocalc/bsfc.php it show a rough idea of bsfc but is pretty accurate, also keep in mind that they show a turbo/supercharged NON intercooled engine at .55 bsfc adding a intercooler improves that to .52-.54. just my thoughts

:edit.... i just thought to tell you also that you can think of atmospheric pressure as 14.7 psi and so every 1 bar or every 14.7 psi (which is a bar [e.g. BARometric pressure])above atmospheric pressure should THERETICALLY double horsepower becuase your are doubling the mass of air per stroke the engine intakes. now it not quite that perfect because of extra ineffiecencies induced due to compressing air ( such as heating the air by which reduces dencity) but it give a general idea of what different boosts will net you in hp gains. ok im really done this time
sorry for spelling i suck at it

 

also as stated earlier that 60-1 turbo map really sucks and they are not very effiecient. the newer garrett t61 is a much better choice for your setup. good price on these. http://www.usedturbos.net/Catalog/New-Turbos/Garrett-Custom-T61.html look at the maps you'll be happy if you get the t61's