Somewhat bummed at 450RWHP, 500+rw torque

[Mikelly]

That post on my profile was just to test the new system when they started enforcing the time slips' date=' its hasnt ran a 1/4 that i've liked yet....

 

I did a 14.7 at LACAR when i first gone the swap done...

 

Now that i have a whine in my rear end and a suspension problem I am giving up on 1/4 times for now untill i get my r200 and my coilovers done....

 

I figure the fastest 1/4 my car can run with the engine is something like a mid 12... unless i get Nitro or forced induction..

 

Yes 30% not 30 Horse..... I've only had the Engine on a Engine Dyno, it put down 372 horse at 5600 rpms and 417ftlb or torque at 3700rpms... so Ill assume its getting 330~ horse to the rears untill get a real dyno run for it.... but then again Gas is killing me so right now its jetted down to a 390 instead of 650... So I am getting better milage... but loosing something like 40% of my power[/quote']

 

My guess is you're down to about a realistic 290Whp or less since you've jetted the carb back. Basically on an auto V8 setup you're gonna lose about 18-20% in driveline losses.

 

Factor in your drag strip times, and yea, I'm really thinking you're probably less than that. Get it on a dyno and tuned properly once you get settled in after your first assignment and then post to let us know. A decent tune will probably be good for some pickup in power and drivability... And as Scottie said, Every Dyno is different, and every operator sets their up differently... Some guys do it by manufacturer spec and have them calibrated properly, and others want the rep of having a more "customer friendy/ numbers generous" dyno... Those are the shops to stay away from. Find someone who uses it as a tool for tuning primarily. Get a decent baseline and then get it to the track.

 

Mike

[dr_hunt]

This is giving me warm fuzzies all over. It won't be long, I think this weekend I should be able to finish up alot of the TT 350 motor. I hard bloked the block and I have some clearancing for the rod bolts to do, the cam is degreed in and it all looks really nice. Figuring pushrod length will be the last real purchase for that engine, then it's on to redoing the down pipes and waste gate piping. Once that's done, I'll drop it and the glide in and get it running. I'm hoping to be done in a month or so then I'll take it to a dyno to get tuning done.

 

I'm lacking;

 

1. New driveline

2. Pushrods

3. Fabbing exhaust

4. Dizzy choice

5. Gauges (EGT, Boost, Fuel pressure, oil pressure, temp)

 

Then if I can lay down some numbers like that on low boost with no tuning, I'd be impressed!

[mobythevan]

Elevation is more of an issue for n/a applications than forced induction applications. As altitude increases, density of the air decreases which decreases the available manifold pressure in a normally aspirated engine. In forced induction applications, the turbocharger or supercharger is able to maintain the manifold pressure (volume of air) at a higher altitude, so horsepower loss is not as pronounced.

 

The turbo or SC is only able to maintain the manifold pressure if it is turned up right? Both cars lose the same amount of manifold pressure for all practical purposes at high altitude, but turbo or SC can be adjusted to raise boost and bring manifold pressure back to the same, but you have now heated the air more so you still lose hp at high altitude.

[Z-Gad]

The turbo or SC is only able to maintain the manifold pressure if it is turned up right? Both cars lose the same amount of manifold pressure for all practical purposes at high altitude, but turbo or SC can be adjusted to raise boost and bring manifold pressure back to the same, but you have now heated the air more so you still lose hp at high altitude.

Yes, I agree you will lose hp, but it will not be as pronounced as in a n/a application where you only have the ambient manifold pressure, in fact at low boost levels it may only be marginal. With elevation you also lose (as a rule) 2 degrees celcius per 1000 ft, so air temps will be cooler. In addition, humidity levels tend to be lower at elevation. So, with an efficient intercooler, 8 psi of pressure in the manifold at sea level may be slightly cooler than 8 psi pressure at say 5000 ft. In either case, at only 8 psi, the turbo is not having to work hard enough to raise the intake air temps significantly. At say 30 psi, then that is a different story since the air is thinner, the turbo would have to work MUCH harder to maintain that 30psi and generate much more heat.

 

Regardless, 450 rwhp in a Z is a handful!! Enjoy

[240ZR]

If you want More info talk to the guys do do Pikes peak...... I think you loose something insane like 50% your horse on the way up..... regardless of NA/SC/Turbo and tuning.. at least that's what i remember from watching the old pikes peak rallies that's part of the reason all the pikes peak cars run insane HP set ups.. b/c they know over halves that power is gone by the time you hit to top.... I forget what pikes peak car it was now bit it was an AWD beast with 700 horse and weighed like 1900 lbs

[proxlamus©]

your in Colorado??

 

holy crap, I need to see this

[John Scott]

Yes' date=' I agree you will lose hp, but it will not be as pronounced as in a n/a application where you only have the ambient manifold pressure, in fact at low boost levels it may only be marginal. With elevation you also lose (as a rule) 2 degrees celcius per 1000 ft, so air temps will be cooler. In addition, humidity levels tend to be lower at elevation. So, with an efficient intercooler, 8 psi of pressure in the manifold at sea level may be slightly cooler than 8 psi pressure at say 5000 ft. In either case, at only 8 psi, the turbo is not having to work hard enough to raise the intake air temps significantly. At say 30 psi, then that is a different story since the air is thinner, the turbo would have to work MUCH harder to maintain that 30psi and generate much more heat.

450 rwhp in a Z is a handful!! Enjoy [/quote']

Altitude density is figured from a standard of 0 altitude at 59 degrees F or 15 C, 29.921pressure, 0% humidity. For direct corrections 5500-6000' needs to be about 3 degrees C. Brrr. we don't race at those temps, though that would figure close to the 20% loss.. I've heard this for years. "Turbos and superchargers don't lose as much at altitude." Sure they do. There is less air to compress! Regardless,The correction factors for altitude, even world record marks, use the same factors regardless of NA or forced induction. Air density is what it is, whether you are running a compressor or not. If you have a blower pulley running XX lb of bost at sea level, or turbo, it will be less up here. Yes you can adjust to make more, with that setting, but then you'd have more boost at sea level with the same setting. You are starting with 80% or less of your sea level horspower, then trying to compress 80% or less denser air to make up for it? Aint gonna happen! No matter how you run it, NA or Forced induction you lose about 20+ % (usually more as altitude density gets to over 10000 on summer days, 12000 has been recorded, temps get into high 90s or low 100s) at our altitude. Check out the times at Bandimere, record times, what ever. Figure in correction factors to sea level. You'll see the turbos aren't favored over the NA cars. In the 10.0-10.99second club at sea level? Welcome to the 10.73-11.79 and likely more club up here. John

[silicone boy]

Yeah, what John said. Man, you guys are smart. The physics part of my brain has atrophied.

[Z-Gad]

Altitude density is figured from a standard of 0 altitude at 59 degrees F or 15 C, 29.921pressure, 0% humidity. For direct corrections 5500-6000' needs to be about 3 degrees C.

AKA standard temperature and pressure.

I stand corrected. I was relating aeronautical experience where an aircraft (let's say a Piper Seminole since that is what I am flying) can no longer maintain a constant manifold pressure of 25" in a climb at say 4500 ft. The same aircraft, equiped with a turbocharger can maintain that 25" of manifold pressure to say theoreticly... 6500 ft. It would just make sense to me that 8psi at sea level is still 8 psi at altitude. My apologies if I have lead anyone astray..

[John Scott]

Zgad, your car ROCKS! Here is a way I look at it. Lets say you live at sea level and have an engine producing 100 hp. You decide to put a turbo on the motor which produces 15 lb of boost, gaining 100% more hp and now have 200 hp. Your buddy has a NA engine that also makes 200 hp. ROAD TRIP! You end up at Bandimere speedway 6000' above altitude. It’s a good air day, but still only making about 80% power due to the less dense air.. Your buddy’s car is now producing 200 x .8 = 160 hp. Take off the turbo and your engine is making 100 x .8= 80 hp. Put it back on, your turbo has to work harder to push the thin air to 15 psi, but makes 100% more hp = 160 just like the NA motor. I in no way want to discredit any of the sea level results. Going 130+ mph in 10 seconds is the same anywhere, and a 10.73 at Bandimere is a lot slower than 10 flat, even though we might run identical set ups. Enjoy the power. John

[Z-Gad]

Thanks John,

Mike

[Pop N Wood]

Don't know that I will argue with what has been said, but I do know WWII aircraft used variable speed superchargers to compensate for altitude. At higher altitudes you can spin the blowers faster to maintain boost pressure without the risk of detonation. Certain models were actually tuned to work best at different altitude bands, and tended to be dogs when operated at the wrong altitude-.

 

So I guess I take exception to some of the statements made above. Take a forced induction engine designed to work at sea level, bring it to altitude and change the blower/turbo configuration and you might get back to your sea level power.

 

Perhaps a more accurate way to state it is a forced induction engine can be retuned to maintain power with altitude whereas a N/A engine has limited ability to compensate for changes due to altitude.

[John Scott]

Perhaps a more accurate way to state it is a forced induction engine can be retuned to maintain power with altitude whereas a N/A engine has limited ability to compensate for changes due to altitude.

I'd buy that, and especially carburetors...now where did I put my box of Jets? Its also not a fair correction factor to say any guy running 11.79 at high altitude will run a 10.99 at sea level. The guys who travel the circuits in a well prepared car will run hard eveywhere. The engine is capable, but as we've seen with the faster members on the site, power is just the beginning. It takes a lot more tire, suspension mods, beefier parts, and know how to apply the power. Wow, we've come a long way with SiliconeBoy's post. Sorry Ben for hijacking your post. With 4" snow on the roads today we can all feel like Silicone boy's beast on the dry roads, Can't wait to see it. John

[Guest Supereri]

If you take an intake manifold at see level and fill it with 8psi worth of air it will have the same volume of air as one filled to 8psi at 6000 feet. The turbo will work harder at 6000 feet to maintain that 8psi, but 8psi is 8psi. The volume of air getting into the engine will be the same (minus diferences in temp). Same amount of fuel will be required as well. The difference will be in that the turbos are working harder at altitude and heating the air up more.

 

As long as the turbo can flow sufficiently at altitude then a turbo car should not be as affected as a N/A car at altitude.

 

Ever hear of turbo normalizing? This is the using a turbo to account for the decrease in air pressure as altitude increases. This allows you to maintain sea level power all the way up until the turbo runs out of flow.

[mobythevan]

If you take an intake manifold at see level and fill it with 8psi worth of air it will have the same volume of air as one filled to 8psi at 6000 feet. The turbo will work harder at 6000 feet to maintain that 8psi, but 8psi is 8psi. The volume of air getting into the engine will be the same (minus diferences in temp). Same amount of fuel will be required as well. The difference will be in that the turbos are working harder at altitude and heating the air up more.

 

I hate to hijack this thread for forced induction talk, and BTW congrats on getting the car finished to Silicon Boy.

 

very simplistic case @ 8psi and you tell me how the turbo makes up the difference without something adjusting the boost:

 

manifold pressure = (sea level) 14.7psi + 8psi boost = 22.7psi MAP

manifold pressure = (~7000 feet) 11psi + 8 psi boost = 19psi MAP

 

Normalizing only occurs if the boost changes as altitude changes as was previously stated. Turn the boost up to 11.7psi instead of 8psi and your normalized for pressure anyway.

[Guest Supereri]

I hate to hijack this thread for forced induction talk' date=' and BTW congrats on getting the car finished to Silicon Boy.

 

very simplistic case @ 8psi and you tell me how the turbo makes up the difference without something adjusting the boost:

 

manifold pressure = (sea level) 14.7psi + 8psi boost = 22.7psi MAP

manifold pressure = (~7000 feet) 11psi + 8 psi boost = 19psi MAP

 

Normalizing only occurs if the boost changes as altitude changes as was previously stated. Turn the boost up to 11.7psi instead of 8psi and your normalized for pressure anyway.[/quote']

 

How does less manifold pressure at altitude overcome the spring pressure of the wastegate, which doesn't change at altitude?

[Guest ModToad]

Total Newb here, but please don't take that too much in account.

 

First off, congrats on the numbers. The Z should be a beast.

 

There's a few things I'd like to bring up though.

 

What cam are you running exactly? I ask, because "big" cams are usually a bad idea in turbo cars. Overlap in a boosted engine will really hurt your spool time.

 

What GN turbos are they? Are these the mystic Stage II turbos? I specced them out before, and almost snagged one off eBay but was outbid.

 

I know there's hordes of people telling you to just "turn up the boost" ... but I'll be the first to disagree. The more you tun up the boost, the less responsive your package is going to be.

 

The Gran National turbos are decently sized, but probably quite undersized for your application, and somewhat outdated. That is if they are the turbo I'm thinking of. Which is the big T3, sort of a clipped version of the Ford 2.3 turbo. I know a few GN guys that have made really decent power out of the older T3s, running close to 30 psi on them. But I also have a friend that managed over 1,000 hp on modern twins. Out of a 3.8. You've probably seen the dyno vid ... I think most of the eWorld has.

 

Running a pair of undersized turbos on a car with a lot of exhaust velocity, especially down low, will do a few things. Your throttle response is probably almost NA in nature. Spool time at wastegate boost (which is what you hit) is probably non existant.

 

Before making any adjustments beyond tuning (ie different turbos, more boost) you should really decide how you want this car to behave on the track.

 

Peak power is only relevant at the back end of the straightaway. Races are usually won coming out of the corners. That's going to demand throttle reponse.

 

Again, I'm making a lot of assumptions about your setup and power curve, so if I'm way off, I'm sorry.

 

If you switch to something like say, two Nissan-spec R33 Skyline RB25 single turbo (ceramic exhaust wheel, ballbearing center section, full boost [16psi max] by 2,000 rpm on a 2.0l four banger). All of this on a T3 flange.

 

Your throttle response will remain unchanged, but the entire power band will be fat. Or phat as the kids say.

 

I've made 312 whp out of one of these turbos on my other car (2.0L 4) and the spool is amazing. I tossed a massive laggy she-devil of a diesel turbo and dropped almost 85whp, but the car IS much faster, way more usable on the track, and the turbo cost me about $100.

 

If you have very deep pockets, the GT series turbos are unbeatable. Massive CFM, low spool time ... but spendy. Very spendy.

 

My other concern lies in the potential for surging the GN turbos under load.

 

The Stage IIs were built to run at much higher boost levels. You may be under the surge line (each turbo is pushing a theoretic 4 psi, way outside of where it was balanced for).

 

Constant surge under load will kill a turbo very quickly.

 

I really don't mean to sound like it's all Doom and Gloom.

 

The Z rear suspension setup is notorious for butt dropping. Most Nissan IRS are. But even in my 200sx (front 280Z suspension, rear 300zx) with 350lb coils, I was getting some butt drop at 190whp. Nothing like before, but 250lb are waaaay too light if you plan to be racing. 6kg (350lb/in) would be the lightest I'd dream of running, and I now run 8/8 (450 front/450 rear). I know it sounds like you're concerned about inducing more oversteer, but in a 2,000lb car with 500+lb-ft of torque on tap, you built the ultimate oversteerer!

 

You have built a brutally fast Z, and I'd love to see this thing run. Turbo V8s make me fall all warm and fuzzy in that special little place.

[mobythevan]

How does less manifold pressure at altitude overcome the spring pressure of the wastegate, which doesn't change at altitude?

 

The wastegate canister is just a diaphram that relies on atmo pressure on one side and manifold pressure on the other, so as atmo pressure decreases so would the manifold pressure to move it?

[Guest Supereri]

How does less manifold pressure at altitude overcome the spring pressure of the wastegate, which doesn't change at altitude?

 

Just ignore me. About 2 minutes after posting this I saw the error of my ways.

[Guest Supereri]

The wastegate canister is just a diaphram that relies on atmo pressure on one side and manifold pressure on the other, so as atmo pressure decreases so would the manifold pressure to move it?

 

Got it...