GT17 or GT20 for K1100 head?
Turbo Mini Forums

Just started to research Turbos for my K1100 head build.

The turbo below, Good or not good ?

https://www.ebay.co.uk/itm/FIT-Saab-9-5-9-3...TcAAOSwLs9abXeg

Wayne

Edited by wayne miller on 5th Sep, 2018.

You take your chances with the cheap Chinese turbos, but in general yes the GT17 is a well proven turbo & will make decent figures. Though if you're looking for a balls out K build then the GT20 may be preferable.
What's your target HP ?

Phil.

WWW.TURBO-MINI.COM

Well I'm looking for a fast road car that I can take to Santa Pod and not embarrass myself Any model numbers for a GT20 Phil ?

200hp? more? where can a GT20 get me?

The GT17 will do 200hp no bother.

Phil.

WWW.TURBO-MINI.COM

If a GT17 will do 200hp what will a GT20 do?

Wayne

What rev limit do you have in mind?

I don't mind how high it revs but I would like the power to come in as soon as possible and last for as long as possible.

Either one will not be a problem.
The GT20 is my preference, but the ease of finding a scrapyard GT17 and simply buying a Chinese Centre housing (which myself and many others have done) is almost certainly a lower cost option.

It looks like you can pick up a GT2052 on ebay for less that £100 and a new Chinese core for about £60. Or there's this for £170 maybe offer £160 ?

https://www.ebay.co.uk/itm/GT2052LS-Turbo-f...3.c100508.m3226

What are peoples thoughts?

Another thing to consider is MED do 7cc 1380 pistons with the valve cut outs. Would they work OK with a GT2052 ?

Actually its 1275 at the moment and they do +20,+40 with 6.5cc or 10cc +60 with 6cc or +80 with 7cc or 11cc. I guess they can machine in the cut outs?

Head blown, I need advice :)

I would be going for an 18cc piston on a 1275 based engine, there is only about 18cc in the k1100 head I recall.

As for the turbo, if you prefer bottom end power I would go with the gt17, and for top end power the gt20 (I opted for a gt2056 though have yet to build the engine, top end power and torque is the priority)

Edited by minimole23 on 6th Sep, 2018.

I believe the only big dish pistons (>12cc) on the market are the forged omegas. Pretty steep at north of 500 quid plus machine work for valve cut outs but you get what you pay for

Don't over look that you can run significantly more compression on the k head, 20 psi on 9 -1 is probably fine,

Comp ratio is swept volume + unswept ÷ unswept

Swept vol - engine capacity divided by number of cylinders
Unswept - piston dish, head volume, gasket volume, piston to deck volume.

18cc Dish

1293 ÷ 4 = 323.25
19 + 18 + 4 + 0 = 41

323.25 + 41 ÷ 41 = 8.88 = 8.9:1 ????

1310 ÷ 4 = 327.5
19 + 18 + 4 + 0 = 41

327.5 + 41 ÷ 41 = 8.99 = 9.0:1 ????


10cc Dish

1293 ÷ 4 = 323.25
19 + 10 + 4 + 0 = 33

323.25 + 33 ÷ 33 = 10.8 = 10.8:1 ????

1310 ÷ 4 = 327.5
19 + 10 + 4 + 0 = 33

327.5 + 33 ÷ 33 = 10.92 = 10.9:1 ????


Im not quite sure how to turn the final math into Ratio but Ive had a go, is this correct and if so which ratio is best suited to a Turbo and what kind of PSI should be ran with each? if that's possible to tell

Wayne

I’m using 18cc pistons with a head gadget volume similar to the BK450 and I calculated compression ratio at 9:1. I’ve seen 20psi boost but mainly 15psi

Edited by Sprocket on 7th Sep, 2018.

The math looks right. As Joe said these heads are a lot more det resistant that using a 5porter. If you aim for around 9-1 you'll safely be able to run enough boost to make well over 200 ponies.

Phil.

WWW.TURBO-MINI.COM

That's Great Lads, so +0.040's with 18cc dish it is :)

Now to deliver these 200 ponies Do I go GT17 or GT20 ? and which Model?

Minimole states GT17 for bottom end power and GT20 for top end power.

What kind of RPM ranges are we talking about. I'm looking for a fast road car that can pin you in your seat and that can also be used to blast down the strip at Santa Pod. GT17 ????

in my opinion, the GT17 is too small. The mass air flow will put the GT17 right in its inefficient region when you consider the engine RPM and expected power output. I was originally intending to go with the GT17 but as I got closer to getting it running, I went with something bigger and i'm glad I did.