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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 12-07-2014, 07:36 PM   #21
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It is what you want because you get lower boost at peak torque than you get at the top where the head is choking so you have a safer curve AND will make more power. Stop and consider it for a moment and you will understand.

You can. Definitely rework it I've done a few wastegate on turbo arrangements and wastegate on cast manifold (rb25/45mm Turbosmart hypergate are popular here) so you can make it flow awesome and it will hold perfect boost within the psi.

What annoys me is the common misconception about boost pressures. If you are trying to stay under a torque limit your boost curve should look opposite to your n.a torque curve which gives a flat torque curve.
You keep the torque below your limit and flat rather than with a big midrange spike to the limit and heaps less everywhere below (waiting to spool) and above (head is flowing less and less as revs rise and it chokes but boost pressure remains the same).

Dann

Last edited by nitrodann; 12-07-2014 at 07:49 PM.
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Old 12-07-2014, 08:10 PM   #22
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Quote:
Originally Posted by Braineack View Post
Would there be any way to weld the ewg off the manifold and rework the outlet?
I'm not sure. It's a plain ole BEGI cast manifold, I think I read about people trying to mount a external gate on them but not sure how it turned out. I don't think I want to mess with that. Hopefully moving the wastegate source helps a good bit.

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Originally Posted by nitrodann View Post
It is what you want because you get lower boost at peak torque than you get at the top where the head is choking so you have a safer curve AND will make more power. Stop and consider it for a moment and you will understand.
Thanks for explaining that, it makes more sense now. I guess I'm too hung up on boost pressure determining the limits of the motor. Once I get the wastegate source moved to pre-intercooler I'll bump up my overboost protection and see how it handles going to redline.
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Old 12-07-2014, 08:29 PM   #23
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"hung up on boost pressure determining the limits of the motor."

Can hardly blame you this is how most cars guys talk about it.
Its very misleading however.
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Old 12-08-2014, 09:19 AM   #24
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If I was creeping to 180kPa, I'd make my lowest boost 180kPa.

Having a torque curve like a centrifugal SCer on a turbo car is weak and lame and something only an Aussie would do purposefully.

you're leaving 3psi off the table between 3500 and Redline. That would probably bring you power up to 240hp/240tq.
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Old 12-08-2014, 11:45 AM   #25
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Pdexta, your first post suggests at the limits of Yellow top, but your sig says ID1000. Which are you running, and did you indeed run out of fuel with the Yellows, or just "almost"?
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Old 12-08-2014, 01:57 PM   #26
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Quote:
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Pdexta, your first post suggests at the limits of Yellow top, but your sig says ID1000. Which are you running, and did you indeed run out of fuel with the Yellows, or just "almost"?
When I initially posted I was on rx8 yellow injectors, a couple posts up I swapped to id1000s. Megalogviewer showed 95% duty cycle and the car wanted to go lean at high rpms even when I kept adding fuel so they were definitely at their limit on stock fuel pressure.
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Old 12-08-2014, 04:54 PM   #27
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Quote:
Originally Posted by Braineack View Post
If I was creeping to 180kPa, I'd make my lowest boost 180kPa.

Having a torque curve like a centrifugal SCer on a turbo car is weak and lame and something only an Aussie would do purposefully.

you're leaving 3psi off the table between 3500 and Redline. That would probably bring you power up to 240hp/240tq.
Yes it might make 240tq at a single rpm, with boost tapering on you can make it from midrange to redline.



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Old 12-09-2014, 04:04 PM   #28
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Ok have you double checked the vac port on the EWG to make sure that the eye bolt or whatever is fully open? Sometimes you can rotate the vac port on the wastegate to limit air flow and increase boost. You might not be getting a large enough amount of air flow through there.
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Old 12-10-2014, 11:36 AM   #29
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I hadn't considered that, I'll take a look at it tonight.

I dropped my intercooler pipe off the. bungs to be welded on it. I went ahead and did one before and after the intercooler so I will have 2 options to play with. I should have it back tonight.
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Old 12-11-2014, 09:51 PM   #30
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Took a small baby step in the right direction I guess. I got my intercooler piping back from the welder and hooked up the wastegate right out of the turbo.

I also checked on ScottyP's recommendation. The banjo bolt on the wastegate was exactly 90 degrees off of a direct flow. I marked the bolt so I could line up the line perfect. Not sure how much difference it made, but any little bit helps.

I datalogged a pull that was considerably better, but still disappointing. You can clearly see boost climbing slower, I'm assuming that's attributable to Brain's recommendation of running a pre-intercooler wastegate source. Having the wastegate open at 7psi, then hitting 14.5psi boost cut before redline sucks, but at least I'm getting closer.

I assume the only way to actually fix it is to correct the wastegate setup like Savington suggested.


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Old 12-11-2014, 10:18 PM   #31
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Quote:
Originally Posted by nitrodann View Post


Dann
except it would be like this:



i'd rather have the red plot all day long and night and year and century.
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Old 12-11-2014, 10:43 PM   #32
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Enjoy your broken motor.
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Old 12-12-2014, 01:37 AM   #33
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What if you run EBC and ramp up the boost to see if you can level off the boost all the way to redline. I really think all this is due to the 90 deg bend at this point it seems it may as well be internally gated. At the WG vent I think it would be ok to have bends but ideally I would think you would want that wg right on the port. (drunk thoughts)
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Old 12-12-2014, 08:07 AM   #34
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Quote:
Originally Posted by nitrodann View Post
Enjoy your broken motor.
Because all 95% of us here with this sort of torque output all have broken motors...

what I'm really suggesting is this:



if you want torque like you're suggesting why are you building turbo setups and not rotrex setups? the reason you install a turbo is torque and area-under-curve, not your pansy *** setup.


I had creep issues back on an old setup:





wanna guess which one of those configurations was better than the other?

it's also funny that my torque output, when holding boost flat, looks closer to what you drew...


having more torque at 7000RPM is much more dangerous than more at 4000RPM. I'd argue that the cylinder pressures at 4K in my examples are still less than that at redline. And that my friend is what bends rods.
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Last edited by Braineack; 12-12-2014 at 08:41 AM.
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Old 12-12-2014, 09:24 AM   #35
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Run it like this


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Old 12-12-2014, 05:24 PM   #36
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Brain.

I have found that in order to hold torque dead flat from peak to redline you need boost to increase past 4500rpm. I have found this tuning stock motors with ms2 rpm vs tps boost control.

Holding flat boost will result in a drop in torque.

There for in order to hover at a specific torque (240 for example) boost needs to steadily increase past 4500rpm by a few psi, I tend to see 16 or 17psi at redline on typical 2560 setups. Some might describe this as creep. Call it what you will.
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Old 12-12-2014, 06:12 PM   #37
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i don't wanna hold torque flat, i want to hold boost flat.
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Old 12-12-2014, 06:19 PM   #38
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Enjoy your reduced performance.
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Old 12-17-2014, 12:46 AM   #39
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Thread sidestep - Dan can you post an ebc table of what you are saying and how you work it?
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Old 12-17-2014, 06:21 AM   #40
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The top row looks like.

95
95
70
12
15
20
25
30
35
40

I'll post one when I have my laptop.

I literally do pulls with 95%DC until it makes boost. Start at 5% from there and add boost until each rpm hits the torque limit.
I pay zero attention whatsoever to the boost or HP until it's done
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