Anyone here with experience tuning a compound turbo setup?

[vwjunkie53]

I'm doing a compound turbo setup on my D24t...  Building the setup is no problem, however I'm not sure how to tune them. I don't have access to a dyno to play with different boost settings between the two turbos.  Pretty much my question is this: how do you know how much boost each turbo should be putting out?  Lets say my overall boost goal is 40 PSI.  The hp turbo could make 20ish PSI and the LP turbo push 10lbs of boost into it, or the hp turbo could be set to make 25psi and the LP turbo could push 7 or 8 LBs into it for the same result.  I know the numbers don't neccesarily add up, but you can get my point here..  You could vary waste gate settings between the two turbos and still end up with the same overall boost level.  Should I be trying to keep my HP turbo towards the lower end of the spectrum of efficiency range (and lower boost) and push more into it, or should I be more towards the middle to higher end of the map and push less boost into it from the LP turbo?

Thanks,
Jason

[RabbitJockey]

post pics of your car first then we'll help you.  i read your build thread on the volvo forum, sweet car and awesome work, i think u posted here too before, right?

if i get time tonight, i'll look at sizing the volvo 2.4 engine and try and help to point you in the right direct, but i've never built a compound setup, i just like reading compressor maps.  check out all the compound threads on here, and the compound thread in the faq, radotd did a really good highly technical write up in there lots of number crunching in his thread and the other threads are pretty helpful as well.

also something that has been bothering me, what is the stock specs of the d24 turbo?  i have read the exhaust side is .36 a/r but what is the trim of the compressor?  i wouldn't think vw used the same compressor on the d24 has they did on the 1.6.

and out of curiousity since i read your signature, what are the specs of the t3/t4 you currently have.

[RabbitJockey]

honestly tho, with the size of the d24 i don't know that a compound is really necessary, what are your power goals?  a turbo that will work efficiently with a d24 is pretty easy to find because of its size being in the range of many diesels and gassers air flow wise.  300 bhp should be cake so long as your pump is setup to make good power at around 5000 rpms or higher

[vwjunkie53]

The original turbo had a .36 or .42 A/R exhaust housing I can't remember... but it was small.  The compressor housing was a small T-3 with a 1-1/2" outlet or so.  My current T3/T4 is a .63 A/R exhaust side with the stage 3 wheel, the compressor is a T4 with 52mm inducer.  Its supposed to be efficient up to 25lbs of boost, I'm pushing right at 30 and the turbo is maxed out.  To spin it any faster to get more boost is just gonna push the drive pressure way up. I have a little bit of fueling left, and think another 10 lbs of boost or so will clean it up.  It may only need 35 to do it
Jason

[745 turbogreasel]

You need 2 LDAs

I'd think that running just below where EGT's really climb at the upstream hotside would get you there.

[RabbitJockey]

so 52mm inducer, im guess it should be a 46 trim to4e

as far as the old one, do you remember the inducer size of the compressor wheel or do u still have it to measure?  i am just really curious what they used haha.

i think your exhaust side should be able to handle more flow, just an upgraded compressor should get u an efficient 35 psi

here is where u should be assuming u have a 46 trim to4e at 30psi, i don't know where u get peak boost i have it set at 2500rpms which is the first highest red dot to the left of the surge line.  the third dot from the right is 5000 rpms so at that rpm ur sitting around 74% efficiency which is very good  and actuall you're probably safe to go a little higher, even tho its not mapped any higher but u can imagine where the lines would some what if it had been mapped.  still not good for 35 psi tho.



the super 50 here looks amazing... this is at 35psi, even a bit of room for more boost if you'd like.  sadly i don't think they sell this turbo anymore.  the regular 50 trim would work too, and thats probably one of your better options, since it'd be an easy upgrade all you'd have to change is the compressor housing and compressor wheel.




heres an hy35w, i know it says hx30e but a few other place shave refered to this as the hy35w map hx30e is apparently its internal name from holset.  looks pretty good with room to grow, u can see its in surge at the beginning but that depends how fast it would spool.  looks like a good cheap option, plus its cool because of its diesel beginnings.




schwitzer s200 looks sweet i dunno how easy they are to find tho




those would be my picks if i were u...

also the borgwarner efr stuff is worth a look too.

heres the numbers i used on squirrel performances turbo calculator.

[mystery3]

honestly tho, with the size of the d24 i don't know that a compound is really necessary, what are your power goals?  a turbo that will work efficiently with a d24 is pretty easy to find because of its size being in the range of many diesels and gassers air flow wise.  300 bhp should be cake so long as your pump is setup to make good power at around 5000 rpms or higher

I think the idea is to have nice smooth power throughout the rpm range? The newer american diesel trucks have compound setups on huge displacement motors so I don't think the displacement of a given motor really comes in to the equation.a

OP, it'd probably be well worth your time to spend an hour on the dyno, it's not too expensive and there must be one within a reasonable drive.

[745 turbogreasel]

The D24 has the same rev characteristics as a 1.6, although having more power masks the effect a bit.
If he can get spooled up by 2300 RPM it will be a super flexible beast of a motor that is gobs of fun to drive.
His T5 tans probably helps with the gear gaps, but the stock turbo spooling at 3000 leaves a lot to be desired while still choking you out a bit up top.

[Alcaid]

heres the numbers i used on squirrel performances turbo calculator.

Your BSFC is way optimistic, it's more in the region of 0.45-0.5 for these engines I'm afraid

Also the VE is not constant through the rev range and 85% is propably at it's best and then decreasing at higher revs.

The turbo you really should be looking into for this engine is the Holset HE221W, they take a serious beating but no good compressor map available.

[vwjunkie53]

Thanks everyone for the replies and especially Trev0rbr for the compressor maps... I have posted here a few times, but I'm usually over on the D24t forum.

I'm not sure what the stock compressor wheel was, though the cold side is a .42 for sure.. I have a picture of it next to the my T66 that I am planning on using for the LP turbo, just for comparison:

The stocker was a complete turd on the D24, it spooled pretty well down low, but above 4k rpm it really choked the engine. With the tiny exhaust housing drive pressure was high, and the tiny intake side didn't help throttle response much either.

The current turbo spools pretty well above 2000 rpm, I can make almost 25lbs of boost by 2500 and its spooled by 3000 easily.  All I probably NEED is a slightly larger compressor wheel/housing, something like a 56mm or so, however I don't want to risk loosing any more low end by having a heavier/larger compressor to spin.  Its right at that point now being a daily driver that a larger turbo I think would hurt driveability.  

The other main reason for doing a compound setup is I already have a new T66 for the LP turbo.  Granted thats way bigger than it needs to be, (66mm compressor wheel with a .70 A/R housing) but I'm guessing its only going to need to push around 10lbs into my turbo depending on the HP turbo waste gate setting to make the desired boost level.  Also, there's a pretty good chance my car is going to be featured in Diesel Power magazine... Having a compound setup would really be awesome/over the top looking setup, and there is pleanty of space to do it.

I did run the T66 on the engine by itself and it did spool, but wouldn't make full boost untill almost 4000 rpm and spooled pretty slowly almost linear with rpm increase. As a driver it was miserable,  but up top it really screamed.  With the t3/t4 already making good boost down low I would think it should be a decent combo for my target boost level.

I did post some pics before but here's one before going to Schied diesel drag race this past summer:


And the engine:




And the race from Schied, my car is up at 6.30 min mark :

http://www.youtube.com/watch?v=956cai5BwxM&feature=autoplay&list=ULKDs8q-pGdeI&lf=mfu_in_order&playnext=1

Again thanks for the help.

Jason

[RabbitJockey]

testing editing

[RabbitJockey]

i came up with the bsfc and ve numbers from reading various how tos on plotting compressor maps, and also by comparing dyno sheets from different cars their hp and what boost level they are at.  some of the numbers may be a bit optimistic, i would still keep bsfc in the .36-.4 range,  but that does not effect where the engine is plotted on the maps, just how much hp they make at that point.  i know that ve and bsfc change a bit with rpm, but i usually do not worry about that because all it does is move the plots on the map slightly left or right.  but i enjoy learning new stuff so if i am wrong please correct me.

what i meant by the d24 not really needing compounds was on the 1.6 they are a small engine and do not rev very high so they do not move very much air with out insane amounts of boost, and it is also very hard to find a turbo for a 1.6 that will make such high boost pressures at such a low flow rate, but with compounds this is simple on a 1.6.  on the d24 that isn't such a problem, like i showed there are many turbos that will work well through out most of the rev range on that engine, and unless more boost is wanted i don't really see the point of going with compounds other than crazy fast spool up that creates crazy tire spin and broken engines.

the compressor inducer size is what i wanna know, the a/r of the housing on the compressor size doesn't mean that much since 35, 40, 45, and 50 trim compressors could all come with a .42 a/r.

[RabbitJockey]

if u want more help with plotting the compounds on the compressor map i can help with that too its just a bit more involved than a single turbo

[vwjunkie53]

Not sure on the factory inducer size, I can go measure it though... Why is this important? I'm not using the stock turbo anyway...

I absolutely realize a correctly sized slightly larger turbo will accomplish the same end result with less work, but like I said, its for the wow factor and I already have the turbo anyway.  Fabbing up the exhaust piping is they type of stuff I enjoy doing, and have all the tools available to do it so why not!

Jason

[RabbitJockey]

the size of the original turbo, i am just curious about because i like to know what they used from the factory to better understand turbo sizing, and also what cars have good donors for 1.6td turbos.  and i thank you very much if you measure the inducer for ;^P

i think if i was doing a compound with your two current turbo i would have the t66 set up for 15 psi, and set up your current t4 for 20 psi above that by making the atmospheric side of the wastegate reference the 15psi from the t66.  or just set them both up for 35 psi,  i think the second option will create faster spool up.  from what i have seen tho it take experimenting to figure out what works and runs the best, especially since you're probably the first person to do this to a d24