Re: Twin turbo.....which ones???

ctwg60 · by ctwg60 on Tue Oct 21, 2008 9:04 pm

I see, I thought as much. If you go high rpm with 2 bar an extra 100cc is neither hear nor there at 7500rpm+. I understand.

How do you go about balancing the pressures between the turbos? Or is it just a case of joining the outputs and directing the flow to the intercooler?

kevhaywire · by kevhaywire on Wed Oct 22, 2008 2:14 pm

I'm a fan of twin turbo on flat and Vee 6s and 8s where you have 2 very defined and seperate turbo banks. Easier plumbing and more exhaust flow for better spool up. But on a 4 pot, I personally don't think the plumbing and other hassle is worth it for the gains, not when a single GT3071R could probably do the same job, if not better.

**mrbeige** · by **mrbeige** on Sun Nov 09, 2008 3:42 pm

I'm just thinking of super quick spool, using two smaller turbos with small exhaust A/R maybe

ctwg60 · by ctwg60 on Tue Jan 20, 2009 11:57 am

JNLRacing wrote:Somepicsof a twin turbo set up on an 8v crossflow longitudinally mounted in my RWD Mk1 that I may get to finish one day

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Long and short if you are going to run 2 turbo's you are best of running 1 per 2 cylinders of identical design and using the intercooler to mix the charge. This way you can get 2 small turbo's to produce 1 bar each giving a compound charge of 2 bar.

The benefits fatter torque curve with quicker spool up providing you get the maths right. Without a restriction of hp at the top end due to a small exhaust housing. Is it worth the hassle if you got the know how it can be fun.

Here's a 1.8t with 2 turbo's recently upgraded the engine and now making 635hp (first car on the page)

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So a bit of an off topic thread resurrection but you obviously used a crossflow head to help with the engine bay configuration of twin turbos on a 4 pot but did you flow test the head before and after porting. Is it right that x-flow heads had bigger ports?

dirtytorque · by dirtytorque on Tue Jan 20, 2009 12:42 pm

Also how much does a x-flow head improve breathing other the standard counter flow arrangment in you experience?

cheers.

JNLRacing · by JNLRacing on Tue Jan 20, 2009 2:40 pm

xflow head flows pretty much the same as the rest of the 8v heads. It's just a lot easier when doing turbo, carbs or TB's as you don't get the heatsoak into the intake.

**mrbeige** · by **mrbeige** on Tue Jan 20, 2009 2:43 pm

In which case, the X-flow head wont have any huge advantage over the counterflow when retaining the standard charger setup?

ctwg60 · by ctwg60 on Tue Jan 20, 2009 2:49 pm

Right then! That was easy. Surprised

Why do you think vw did a cross flow 8v? scratch

**mrbeige** · by **mrbeige** on Tue Jan 20, 2009 3:41 pm

ctwg60 wrote:Right then! That was easy.

Why do you think vw did a cross flow 8v?

Packaging I'd imagine, and also variations in performance/economy based on heatsoak. I would guess that all later 8v engines used cross flow.

ctwg60 · by ctwg60 on Tue Jan 20, 2009 4:22 pm

Yes I came to the same conclusion, it also allowed them to run plastic intakes! Wink

The 2.0 xflow engine also produced the same torque and power as the cflow but produced it 800rpm lower for torque and 200rpm lower for power but I think this can be contributed to other changes they made at the same time. So I think I'm not going to be the one to try to disprove anyone by doing a xflow 8v G60 engine.

Oh well my life just got a lot simpler! Smile

JNLRacing · by JNLRacing on Tue Jan 20, 2009 5:50 pm

^^^^ the lower rpm power delivery is down to the manifold configuration having longer runners. making it a more suitable town car.

ctwg60 · by ctwg60 on Tue Jan 20, 2009 5:53 pm

JNLRacing wrote:^^^^ the lower rpm power delivery is down to the manifold configuration having longer runners. making it a more suitable town car.

Yep, and I read in a book that they ran a shorter rod as well lowering the rod to crank ratio but I've never been able to substantiate that.

dirtytorque · by dirtytorque on Tue Jan 20, 2009 10:34 pm

I guess the (cost/gain)* (agro) factor is unappealing but it is a much better engine configuration.Cold air at front,hot air coming out at back.shorter pipe work...

If it wasn't for that pesky alternator on the g60...

**mrbeige** · by **mrbeige** on Tue Jan 20, 2009 10:52 pm

dirtytorque wrote:I guess the (cost/gain)* (agro) factor is unappealing but it is a much better engine configuration.Cold air at front,hot air coming out at back.shorter pipe work...

If it wasn't for that pesky alternator on the g60...

Can't you mount the alternator underneath the charger? Maybe where the power steering pump is and then run an electric one instead?

junkie · by junkie on Tue Jan 20, 2009 10:56 pm

Just seems loads of work for little gain, prob get pretty much similar power levels put maybe less variation of the power depending on the heat gain issue????