Beaten to it by Borg Warner - interesting paper on regulated two stage turbocharging

Found some interesting information on the above last night - basically in employs two turbos of different sizes; one to feed the engine at low speeds / throttle opening, and the other, larger one to cater for the top end. Balance between the two is achieved by progressively bypassing the flow of exhaust from the smaller to the larger unit as engine speed and load increases.



Basic overview Here, more in-depth .pdf can be found here

I fancy doing similar from scrapyard parts; although was planning on using two turbos of the same size and a flapper valve on the compressor side.. it's nice to at least know the idea is sound and to find some more information

Given some of the information in the paper and 3K Borg Warner's longstanding relationship with VW; I wonder if we'll see this technology replacing the 1.4TSI engines in the future?

Downsized, highly boosted engines seem to be the way everyone will go (in the interests of fuel efficiency).. interesting stuff

 

Is this similar technology that BMW employ in their 3.0 twin turbo petrol and diesel engines, and now in the new M5? I agree with you that we will many more small displacement turbo engines cropping up. The end is in sight for large capacity engines I think!

 

sequential turbot

RX7 and supra had that too i think... so could be an idea to pilfer parts from

 

I can't see vw replacing the tsi stuff with two turbos. The supercharger gives you the low down boost early on which the small turbo just can't do as well as a supercharger. They are also clutching the supercharger so it's not sapping power when not needed.

 

I think so - that BMW 2.0 twin turbo is an especially impressive piece of kit

Yup, looking at the Supra setup it seems similar, although somewhat more convoluted. One difference appears to be that the majority of the waste gas from the primary turbo goes straight down the exhaust, rather than through the second turbo..

This is true, however I think VW are known to be dropping the TSI engine, and the use of a pair of turbos could potentially make for easier packaging as well as better economy as there are no parasitic losses during boost generation

Don't suppose anyone can suggest any decent vehicles for scrappy - sourced turbos? I was hoping a K03 would do as the secondary on a 1.3 16v engine, however I think it's a bit big unless I can persuade the engine to rev to 8-8.5k (which means cams, and more expense). Shame as they're dirt cheap since everyone wants K04s. At a bit of a loss for the primary turbo too; was thinking about Smart car units, however they seem to be integrated into the exhaust manifold and I can't find any compressor maps anywhere..

 

Something like a diahatsu charade or totyota starlet turbo will probably do as a primary. If you run it sequential setup style it should also help spool a k03 sooner anyway.

 

Cheers; think I really need something smaller than a Charade or Starlet turbo though since it needs to operate over the 1000-3000rpm range; which on a 1.3 litre would have similar peak inlet flow to a 700cc lump at full chat.

I agree about the earlier spooling of the larger turbo, however the max airflow from a 1.3 @ 6500rpm is just inside the low side of the main efficiency island on the K03 maps I've found.. meaning that at any lower engine speed / load it'll be well outside it's peak efficiency range.

I'll look into turbos on the small jap stuff; always pays to know what's about

 

I think Daihatsu may have made a smaller turbo 1.0 somewhere along the line. Or you could look into motorbike turbo's such as the cx500 or gpz750 turbo. Or an XN85 turbo. All of these are as rare as rocking horse poo or hens teeth.

 

Smart cars? Arnt some 3 cyl 600cc turbos? or something like that

 

A few of the Polo G40 boys run ko3 turbos and those work well on a 1.3 with a 8V head. I did one using a ko3s that wasn't mapped to run a turbo and that came on around 3.3k.

 

Cheers; will look into the Daihatsu effort. I've thought about bike turbos but their inherant rareity means they'd probably be more expensive than a new Garrett or KKK.

I think so; however it appears that they run integral turbo and manifold assemblies, making adapting one to another application a bit of a pain..

Thanks; the amount of air the compressor needs to flow is still a bit open to debate at the moment, so perhaps a K03 might just do if I don't want to run loads of boost.

 

Suzuki Cappuccino 660cc 3cyl turbo, worth a look for your primary turbo??

 

i had a T25 on boost at 3.5k on a G40, a remapped ko3 will come on song around 1.8k

Compound charging is what i was going to do using a Ko3 and tdo5 on an ABF......search 'marc compound charged' on youtube to see a set up

 

Thanks - I shall look into them. Not sure how easy it might be to source one, though.

Cheers - you say a "remapped K03" - are you simply referring to the engine ECU being remapped to accomodate the different charger, or some alteration to the turbo itself? What boost would said K03 be running? I'm looking for around 1.2 bar which I understand is about as much as you can push them (depending on speed) before losing compressor efficiency.

Had a look at the video - very interesting


Talking of Diesels, I've heard it mentioned that diesel turbos aren't suitable for use on petrol vehicles; the two reasons I've heard mooted are that they have too small an operating speed range and can't take the higher EGTs of the petrol engine. I think the first issue might not be a huge problem on a compound / sequentional setup, and that the high EGTs might not be a problem providing I go with a turbo that also has petrol varients (and hence hopefully has a turbine wheel that should take the elevated temperatures)... can't find any compressor maps though

 

vw transporter 2L tdi biturbo engine...180 hp!