How to make the smoothest running, most efficient CA

[Spectre_240sx]

I've been thinking about it for a while, and I don't know if I really need a high horsepower monster. I can see myself sitting on top of 250 and being able to do anything I really want to do. Now, 250hp is easily achievable. I know that, but what can be done to make one 250hp engine better than another? I'm thinking things like a higher rev range (it can come in handy sometimes), better throttle response, lowest amount of lag possible, smoothest running possible.... The sorts of things that are often overlooked by garage tuners.

[BoroBoroS13]

Sounds like your looking for what I want... Reliable, smoth power band, quick spool up, and responce. I think the best way to do it is by using a GT25R or GT28R. Basicly these are T25 or T28 turbos that have been tricked out by Garrett so they have less components and ball bearing center sections. I want to go with a GT25R cause I want some crazy responce and spool and dont want more than like 230hp (Touge car so I dont need big power till the straights and 230hp is more than enough). But with a GT28R you can get a lot more power but there will be a little more lag.

[float_6969]

Thats what I'm building for. If it works right, I'll let you guys know what I did. Until then, I'm keeping it a secret...

[paul_s13]

Getting the bottom end balanced up and a light flywheel makes a nice difference, the engine just sounds much happier at higher rpm's.

Also just matching the inlet ports and inlet manifold to the plenum is a good move and its very easy and quick to do.

[anumeric]

Not to be rude but you don't seem to know what you're talking about. The GT25R is a top-end turbo, not known for quick spool and response. The GT28R on the other hand is a big bandwagon turbo ever since SCC did an article about how godly it was. It does indeed spool better than the GT25R and provide better power than the stock T25 but only marginally when compared to the S15/S14 BB T28--which is where it's at. It has spool, flow, and price all in one package. It's quicker to spool than the stock T25 and is capable of around 300hp, maybe more depending on your management setup and ability to tune.

Take a look at http://www.nicoclub.com/zerothread?id=65174.

Edit: This post was actually made by "SeVa-S13." Forgot to log my friend out. Direct all hate at me.

Modified by anumeric at 12:31 AM 9/26/2004
Modified by anumeric at 12:31 AM 9/26/2004

[iliketocrash]

things that often are overlooked is suspension and such things. go with that and you'll have a well rounded car which most people don't have. some things that people do to get a little faster spool from a turbo is having the compressor housing honed/extruded. depending on the turbo it can help quite a bit.

[BoroBoroS13]

Im sorry SeVa-S13 but I do know what im talking about. The GT25R that you are thinking of isnt the one I am talking about at all. Im using the labels that Garrett uses for their turbos, not what people call them on the forums. Oh and the turbo SCC made famous is the GT28RS not the GT28R.

Here are the specs on both turbos, if you want maps I can get them too.

Turbo Unit/Turbine Wheel/Compressor Wheel/ Flow Capacity GT25R/53mm/54.4mm/240HP GT28R/53mm/60mm/290 HP

[anumeric]

The 28 is my fault--I had assumed you misnamed it and were thinking of the RS. But if you say the 25 is called differently, then what do we all talk about when we discuss the 25R?

[iliketocrash]

gt25/40r?

[Looneybomber]

Thats what I'm building for. If it works right, I'll let you guys know what I did. Until then, I'm keeping it a secret...

Hmm. What should I do? Post pics of your car and the parts all over the garage? Should I let the secret out of the bag? How can they all have good power right off idle and be fully spooled early on in the rev range and scream right on up to 9k? Ok ok, I won't tell. However I still say it's too much dude. I'm scared. Though I do want to drive your car when you get it finished.

Oh specter, BTW reciprocating mass is bad, try to get rid of as much of that as possible. Also efficiency and all'round performer are 2 totally different things (if you don't understand what i'm talking about, think diesels). Your title doesn't coincide with your post.

[float_6969]

Dustin, you'd better keep that trap shut man! Hehehe. It won't blow up, I promise.

[CA19DET]

S15 Turbo & HKS Actuator, SSA manifold, 3" Downpipe & 3" Exhaust, HKS O2 pipe, FMIC, 256* In/Ex Cams & Springs, 440cc Injectors, 300ZX AFM, S'AFC & Enthalpy (SecretServices) Rom Tune, Walbro 255Hlph, NISMO clutch cover & Disk

[Spectre_240sx]

when I spoke of efficiency I was thinking more of the most efficient use of the power that a car has. Like using a lightweight flywheel so that the power goes straight to the wheels rather than into the flywheel, or knife-edging the crank so that there's less windage slowing things down in the engine. I suppose I could have been more accurate, but I hate summing it up into a subject anyway

[biosehnsucht]

Anyone know what the ballpark figures are for things like knife edging the crank and the downsides of it (if any) ? same for "balancing the bottom end" and what exactly does that mean? I assume it means to do whatever machining is necessary to make sure that all the rotating / reciprocating bits are equal to each other..

[float_6969]

When you have the bottom end balanced they weigh all of the rod/bearings/wrist pin/piston/rings of each set. After they find out which one weighs the least, they remove weight from the others so that they are all equal. This is usually done to within half a a gram. Depending on the type of crank, they may also spin it up with the rods and ect. attached to make sure that the counter weights on the crank are still accurate. ANYTIME you change something on the bottom end (rings, bearings, pistons, rods) you should have the bottom end balanced.

[Spectre_240sx]

Where do you go to have things like this done? Do most tuner / speed shops offer this service or do you have to send all the parts out or something?

[BoroBoroS13]

Your gonna want to find a really good machine shop that builds race motors and has a really good rep. Its not a good idea to cut corners and go cheap with this kind of work.

[Looneybomber]

What exactly does "knife edging" mean. Here i have attatched a pic of crank and stuff. Circle on it what you would knife edge and what you would do to it.

BTW the setup you see there is good for 16,000 rpms

[float_6969]

Read this... http://www.importperformancepa....htmland this... http://www.autotech.com/catalog/crank.htmthis one really shows what it is http://forums.vwvortex.com/zerothread?id=1579033still not done...http://www.nissanperformancema...erds/I think you guys should get the point now...http://www.honda-performance.c...age=5

[redamnavit]

Anyone know what the ballpark figures are for things like knife edging the crank and the downsides of it (if any) ?

The fourth article that float posted explains it. To summarize, the crank's counterweights have to have a certain amount of weight to do their job. Remove too much and the engine has to fight excessively on the compression stroke.

Its not advertised as often (maybe because it doesn't look or sound as sexy) but you can also have a crank bullnosed. Instead of a knife edge on the weights you get a smooth half-round.

[Looneybomber]

Ahh geez, Come'on float. After all that reading I found out I already knew what it was and that crank i posted is all ready knife edged basically. However it's a pretty dull knife But it looks like the counterweights havnt been done. Ah well must not be a big deal to get it knife edged.

Modified by Looneybomber at 4:06 PM 10/4/2004
Modified by Looneybomber at 4:09 PM 10/4/2004