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Login to post Forums » Grassroots Motorsports » More area under the curve. Turbo conent.

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Jan. 10, 2011 1:42 p.m. cxhb HalfDork

Im bored at work and brainstorming here. I DO plan on going turbo with the fun car when the money is right but I want to do all my homework beforehand.

Im looking for very conservative numbers, I know a lot of honda guys are all about big power in the high end and usually do get lots and lots of hp, but thats not really my goal. I want more usable power, specifically a broader torque curve.

My question is, what can be done to make a flatter torque curve on a turbo engine?

Little/no overlap in cams?

Somewhat higher compression than average?

All suggestions welcome!
Jan. 10, 2011 1:44 p.m. MrJoshua SuperDork

Small or BB turbo slightly bigger than that. Very good manifold. Higher compression. Aggressive tuning. Just make up your dyno numbers. Etc...
Jan. 10, 2011 1:54 p.m. cxhb HalfDork

can a lot of the "peaky" nature be smoothed out by tuning?
Jan. 10, 2011 1:58 p.m. carguy123 SuperDork

Most of the peakiness is caused by the level of boost itself. If you don't have boost you don't have the power. If the boost comes on suddenly then so does the power.
Jan. 10, 2011 2:01 p.m. Zomby woof Dork

Small turbo, more cam = better low RPM boost performance, and more power with less boost.
Jan. 10, 2011 2:12 p.m. 92CelicaHalfTrac SuperDork

cxhb wrote:

can a lot of the "peaky" nature be smoothed out by tuning?

Yep, and easily. Most decent EBCs will allow adjustments to the "gain," which will effect how the turbo spools up. You can have it all at once, or a gradual smooth spoolup for a nice un-violent powerband.
Jan. 10, 2011 2:18 p.m. kb58 Reader

Here's my dyno curve of a Honda K24 using a twin-scroll GT3071 turbo. Note the very wide torque curve. 9:1 compression, 91 octane gas, RBC intake, and stock cams. The entire design was driven by the goal of making a wide torque curve instead of the infamous doubles-the-horsepower-in-1000rpm type of car.
Jan. 10, 2011 2:44 p.m. cxhb HalfDork

kb58 wrote:

Here's my dyno curve of a Honda K24 using a twin-scroll GT3071 turbo. Note the very wide torque curve. 9:1 compression, 91 octane gas, RBC intake, custom exhaust, stock cams. The entire design was driven by the goal of making a wide torque curve instead of the infamous doubling-the-horsepower-in-1000rpm type of cars.

THIS is what im looking for. Albeit with smaller numbers. I honestly would be happy with 250hp and a flat torque curve. anything above that and its just wheelspin. I wonder how hard it would be to get a similar curve with a 1.6L...

Also, totally random and PROBABLY dumb question, but by EBC im assuming you mean electronic boost controller right? Im totally new to the world of forced induction, so If I want to use an EBC does this mean Im limited to an internal wastegate?
Jan. 10, 2011 3:09 p.m. kb58 Reader

Sorry, an "RBC" is Honda's part code for an intake manifold off a different model Honda that flows better than the stock setup.

For a small displacement engine I don't see why you can't do the very same. (250/400) * 2.4 = 1.5 liter equivalent. You just have to use a smaller turbo than all the Honda guys tell you to. Better yet, have them show you dyno curves until you see one you like, then copy his setup.
Jan. 10, 2011 3:14 p.m. procainestart Dork

cxhb wrote: Im totally new to the world of forced induction...

Buy or borrow this book:

Street Turbocharging: Design, Fabrication, Installation, and Tuning of High-Performance Street Turbocharger Systems
Jan. 10, 2011 3:28 p.m. MrJoshua SuperDork

Miataturbo.net has lots of 1.6 turbocharged cars. If you like to stay out of fights, read lots and lots before you post anything.
Jan. 10, 2011 3:54 p.m. 92CelicaHalfTrac SuperDork

cxhb wrote:

Also, totally random and PROBABLY dumb question, but by EBC im assuming you mean electronic boost controller right? Im totally new to the world of forced induction, so If I want to use an EBC does this mean Im limited to an internal wastegate?

Yep, Electronic Boost Controller. And nope, you can use it with any kind of wastegate. I'm not a fan of internal wastegates, personally, but if they get the job done, they get the job done.

I'm using a Greddy Profec B Spec II EBC with a Turbosmart UltraGate38 and a welded CT26 turbo at the moment. Works great.
Jan. 10, 2011 4:04 p.m. Raze Dork

other thing to consider is exhaust pre-post turbo, you can do fun things with spool on turbos and at the same time change your low end response with pre-turbo exhaust manifold changes, and the same goes with post turbo. This is usually cheaper and easier than cams, but tuning will be critical again as most have said. Just depends where you want to play around.
Jan. 10, 2011 4:27 p.m. DILYSI Dave SuperDork

High CR, small turbo, minimal piping, etc. I'm putting just under 200 ft-lbs to the ground @ 2500 RPM out of a 1.6L
Jan. 10, 2011 4:34 p.m. pres589 HalfDork

Dave: What's fuel economy like with your setup? I remember catching some of your build thread but don't remember what turbo you're using, what are you going with now?
Jan. 10, 2011 4:37 p.m. corytate New Reader

d16 or b16? with the lower cr 1.6's you can probably up the cr to 9 or 9.5:1 running about 10psi and you'll be making good numbers and maintain what low end you have. if its the b engine you'll definitely be able to handle a good amount of boost, don't know much about the d engines though. as said above, though, stick with a smaller turbo, maybe even spend some real money and get a twin scroll turbo to keep that low end and maintain power, because you'll be able to spool up faster and still run higher boost. a more open downpipe can also help a turbo spool up quicker, and so will the amount of piping you have for your intercooler setup.
friend with a mazdaspeed protege switched to a front mount from the side mount intercooler setup he had and lost ALOT of his low end grunt, but you really need a front mount if you want to run a lot of boost.
as said above, you would probably come out the best setup if you found a dyno graph you like and copy the setup as closely as you can. make sure it's with your engine though, there are pretty big differences between the b and d 16's and even between the single and double ohc engines with the families.
Good luck!
Jan. 10, 2011 4:43 p.m. DILYSI Dave SuperDork

Turbo - T25 running @ 10 psi.
CR = 11.5:1
Fuel = E85
Mileage = No idea, but quite poor I'm sure.
Jan. 10, 2011 4:48 p.m. pres589 HalfDork

Ha, I forgot about your CR being that high, and I'm sure with E85 and enough fuel to keep the detonation away the mileage is indeed "quite poor".
Jan. 10, 2011 4:50 p.m. kb58 Reader

Yea, I was about to mention fuel. Decide up front if you're going with petrel or E85 - BIG difference. Most of the time the people who tell you to run high compression are assuming you'll run E85. In the majority of the US it's just not very available and has to be hunted for. I considered it for about 5 minutes and decided I wanted to be able to drive anywhere, and not have to plan out a route each day to intercept E85 stations. You can get crazy big hp numbers on E85 but on regular gas it'll be quite a bit lower. If you're going with regular gas you can run maybe 10:1, but most people run lower - it's engine-dependent.

Oh, then there's deciding to go with E85 and going to a trackday event. My brother's Locost-type car uses nearly 50 gallons of regular gas on a track weekend; if he used E85 it would have been closer to 70-80 gallons. Now imagine if the nearest E85 station to the track is 50 miles away... Gonna drive in with a tanker behind you? Just sayin', consider your goals.
Jan. 10, 2011 5:02 p.m. corytate New Reader

kb58 wrote: Most of the time the people who tell you to run high compression are assuming you'll run E85. In the majority of the US it's just not very available and has to be hunted for. I considered it for about 5 minutes and decided I wanted to be able to drive anywhere, and not have to plan out a route each day to intercept E85 stations. You can get crazy big hp numbers on E85 but on regular gas it'll be quite a bit lower. If you're going with regular gas you can run maybe 10:1, but most people run lower - it's engine-dependent.

yeah i was assuming he would be running premium pump gas
if you're going to run e85 make sure the tuning is spot on and you get some giant injectors because you'll be basically dumping it in
Jan. 10, 2011 5:04 p.m. bigbens6 New Reader

Little turbo, thats the key realistically, higher CR is good for overall power, but from my reading it has little effect on spool or boost threshold, then again every little bit helps and higher CR will also mean better throttle response and better off bost power/tq production.
Jan. 10, 2011 5:46 p.m. kb58 Reader

There seems to be two camps when it comes to how much compression to run in a forced-inducted car. One says it should be no more than about 8:1 (Corky Bell, for example), while the other group says you can go as high as 12:1 "with good tuning." You picks your number and you takes your chances.
Jan. 10, 2011 5:48 p.m. bigbens6 New Reader

I think with todays tuning solutions 8.1 is pretty weak, though i would not go above 9 myself... depends alot on combustion chamber design and ic etc...
Jan. 11, 2011 9:16 a.m. 92CelicaHalfTrac SuperDork

I have 7.8:1 compression, with a fairly large turbo, and i'm still hitting full boost before 3000rpms. This on a 2.2 litre 4-banger.

There's really far more to the discussion than what's been discussed so far.

Exactly what motor are you going to be using? Do you really want a ton of low-end tire-shredding torque? Or are you going to be running gigantic tires like Dave?

On street tires, there's nothing enjoyable about an EF Civic making 250wtq @ 3000rpms. Nothing.
Jan. 11, 2011 9:26 a.m. dsycks Reader

Why go with the 1.6 when what you want is twist? Go with the most displacement you can easily swap in and keep it simple.

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