Mythbuster: continuing project thread of my 1303 '75

[70Turbobug]

Congrats Wally! That is really awesome! That curve is amazing - actually it´s not much of a curve,more like a rocket start.. If I read the log correct,your max boost was 1,46 bar? What springs are you running now? Do you think that your valves were beginning to float? Richard sent me an interesting link on springs they use in drag bikes. http://www.psisprings.com/index.php?...ask=view&id=20.

[Sandeep]

Thanks for the detailed information and posting the log.

I have 370lb springs in the twin plug heads, but they will lose some pressure as they are run, estimating 10% so should end up at 330lbs. I told Len that I would not be boosting past 20psi though, or revving past 6500 rpm.

I based my turbine selection (Garret GT3076R, 0.63 hot side) on information provided mostly through Subaru boards, as the STI engine is 2457cc vs my 2413cc, and I had no aircooled data at the time. It is 4v vs 2v though as far as valves per cylinder is concerned, but I think the 2v per head should have better intake velocity.

The .63 is supposed to provide better spool but not as much top end as the .82, which is the next step up for the Garret GT3076R.

I was looking at an honest 300 FWHP motor, not stressed but living a comfortable life, but it looks like 350-375 FWHP should be more realistinc.

Thanks for all of the information, your motor build has been very educational and inspirational and I hope to be able to join your ranks in the coming months.

Sandeep

[Wally]

Originally Posted by 70Turbobug

If I read the log correct,your max boost was 1,46 bar?

Not really: that point was just where the cursor was at that moment. More random therefore. Boost was about 1.0 bar at 4K, then climbing further to just over 1.7 bar at around 5K, then tapering to 1,5 at 6K and further down to 1,4 bar at 7K.
On the road, in 4th, 1 bar is reached at 3600 rpm if its not too hot outside.
Just follow the horizontal lines on the y-axis at the right. The scale is there. If you can read plots, it shouldn't be too hard to see what is reached when

What springs are you running now? Do you think that your valves were beginning to float?

Originally Posted by Wally;

The ripple after 6200 rpm is valve starting to bounce of the seat imo...

I use the Berg dual springs with Ti retainers. I will try to install my CB650's over winter. That will sort that out.

@Sandeep: I think every motor is different and maybe I have restrictions elsewhere, but boost is tapering despite my EBC set at closed-loop... so I suspect my 8cm² turbine (~0,63-ish I think) is just too small for these kind of hp. My back pressure readings kinda confimed this imo.
For an even bigger engine like your comming 2413cc, I would surely get the 0,82 A/R if you had free choice. You may loose some spool as opposed to the 0,63, but you already got that covered by the 200cc's more you have over mine...
I also looked heavily at what Subaru owners use (hence my DOM3 I got off a us Suby owner) and this combined with my current experience, I would surely get the 82 for your 2413cc. Our engines are just more responsive by themselves somehow I think.
You don't want to know what my next turbo/turbine size will be...

[Sandeep]

I'll keep the .82 in mind before I take the .63 out of its new packaging

My guess on your next turbo is a minimum of a GT35R (GT3582) or somewhere there abouts ... 400 to 650 HP on a minimum 2.0l.

You got to 400hp quickly with this build so I'm thinking ~500hp minimum is your next goal

Sandeep

[Wally]

Originally Posted by Sandeep

I'll keep the .82 in mind before I take the .63 out of its new packaging

A _very_ nice compromise would be the Tial stainless housing Its ~0.78 A/R iirc and saves a lot of weight on the right side of the car...

My guess on your next turbo is a minimum of a GT35R (GT3582) or somewhere there abouts ... 400 to 650 HP on a minimum 2.0l.

You got to 400hp quickly with this build so I'm thinking ~500hp minimum is your next goal

Sandeep

I have no hp goal, but only seek the 'perfect' turbo.
Its not anything like you mention though...
When (if?) it gets here, I'll sure let you know/show you. It is meant for after an engine upgrade tbh, but it would be interesting to try it on the 2,2 first and see the difference later on the bigger engine (which will take a year or two probably..).

[Wally]

Just finally got confirmation that the new turbo had been produced and a small batch was shipped from the Borg-Warner plant to Full-Race.com which just shipped one out to me

How big? Its a T4 Twin-scroll with a compressor in between a 35R and a 40R, so its fairly big

Also got a second hand, but unused waste-gate from evil bay, but need a second one because of the twin-scroll lay-out.

[Bad bug]

Originally Posted by Wally

Just finally got confirmation that the new turbo had been produced and a small batch was shipped from the Borg-Warner plant to Full-Race.com which just shipped one out to me

How big? Its a T4 Twin-scroll with a compressor in between a 35R and a 40R, so its fairly big

Also got a second hand, but unused waste-gate from evil bay, but need a second one because of the twin-scroll lay-out.

Hey wally you finally going to do the twin scroll turbo setup. Glad you are because i want to use a twin scroll Holset on my 1835cc engine once i build it.