Supercharger on a 280Z

[HSVSUX]

With pansy little turbos eg my mates VG30DETT, we're talking maybe 0.5 sec or so....not much. But when you're talking large turbos, we're talking seconds. Two good examples are two mates RB20 powered skylines, both with different large turbos. Both of them will take around 2seconds to start making useable boost.

That sort of lag shits me to tears. Sure the cars are fun being silly fast and all, but they're almost useless when it comes to the corners, because it simply wont make the power you want when you want it.

Example 1: Brake hard for the corner, even get hard on the power very early in the corner and it still wont make good power until you're out the other side.

Example 2: We were out in the middle of nowhere and decided to pull a donut.....drop it in 2nd, rev out to the limiter almost imediately, so back of the accelerator to get it off the limiter, foot down again, oh look its dropped off boost, then bogs down before it can build boost again.

Basically the same happens in corners. Sure it's an extreme example this car having a rather large turbo and all.....but the same happens with pretty much any turbo setup.

Having come from the 260Z where I am some what spoilt for throttle response, any amount of lag shits me to tears, even the tiny little bit in my mates Z32 tt.

Cherio

Mate, you need to drive some more turbo cars................

seriously

[Murph]

I've driven plenty bloke. Like I said my example is toward the laggier end of the scale, but never the less still applies. Sure some may be happy with how a turbo cars drives, I am not. That's my opinion and I am entitled to it.

[kjones]

Holy moly, I turn my back for a couple of days and look what happens.

Yeah look what happens... we have a great conversation until you arrive with incorrect information and wrong quotes! Then try to turn a great thread into a turbo vs supercharger argument! Both a turbo and a supercharger have their place in the high performance world, it just depends on personal preference and the desired end result... Please don't continue along the lines that you started... it has no place here.

Are you kidding? I wouldn't be running anything over 7psi without an intercooler. And why wouldn't you use one? Its free power, it makes detonation less likely, etc. Especially considering positive displacement superchargers have horrid adaibatic efficiency compared to centrifugal compressors.

MANY people run more than 7 psi of boost with no intercooler for many reasons, from simplicity to cost to a whole host of other reasons. My supercharged 280z runs 13.5 psi on pump gas with NO detonation what-so-ever... MAT are monitored closely and have stayed within reason. While intercooling will help, this is an R&D project and I prefer to make small incremental changes so I can accurately analyze the results of EACH change.

How does an external bypass dump more air on throttle close than an internal one? especially as the internal one has no alternate route, but the external one does.

Did I ever say one dumps more air than the other? Ah No...

I was trying to understand what Datto-Zed was proposing and pointing out the challenges that he would face in tuning... I know this from experience based on my findings

Tuning accelleration enrichments depends a lot on the engine management. It was very tricky using a megasquirt, and very easy using an autronic. Good datalogging (AFR, MAP, RPM, TPS) make this no more difficult than any other part of tuning the car.

I disagree... tuning around the bypass has been one of the biggest tuning challenges we have faced.

I was running my 240Z with a L28 supercharged using a toyota SC14 (1GGZE) supercharger. This supercharger is WAY too small for the engine so only gave me 5psi. There are so many factors to consider when you are trying to decide about the viability of superchargers for your application:

- power output

- power delivery

- packaging options (phsyically mounting the bits)

In reality, you will be able to get basically whatever power you want from either a turbo or a supercharger setup with enough development. Horses for courses.

That is probably the most sensible paragraph that I've read from your posts... finally!!!

Oh and my final thought (just because this point annoys me something fierce), turbo-lag is a storm-in-a-teacup for street/circuit driving (only people who require instant response in rapid on-off applications are rally drivers). Seriously, grab the next gear down ffs! Gone!

Dave

Well, sorry, but the whole depress pedal, wait, hold on, no wait I gotta grab a different gear thing isn't what I was looking for... Most people who are looking into supercharging are of the same opinion. While there are things you can do to reduce turbo lag (and let's not go there in this thread), reality is it can't be completely eliminated. My goals were to have good power that was there all the time. I didn't need to have a ridiculous amount, just good respectable power... I wanted to road race with my configuration (although its great on the street too). I wanted predictable throttle response through a turn on a road coarse with the power being there when I needed it. If I needed to feather in the throttle at the apex, I want the power to be there when I do so.

I've driven several turbo cars on the road coarse and they were all a handful to drive and as a result I was slower than when I drove a similar car with less power in a NA configuration ... why? because I was able to drive the NA much more smoothly.

So there's my opinion...

BTW I love turbo's too... I'm building a turbo Z right now... with a different set of goals and intended use!

The merits of supercharging have their place in any performance application... that is reality. Quite frankly, if more people got a ride in my car, I'm sure it would make you reconsider several of your points...

This will be my last post on this thread... you guys have fun...

[Dreco]

That's great to hear!

I'd love to see the performance of one of these babies on a Rebello or Sunbelt motor!

Ken

Well, I just so happen to have Rebello's 3.0L stroker motor. I'm running a 9.8:1 compression ratio. Not sure if that supercharger would be too much boost (i've heard it just really depends on internals, and how well the motor was built).

[kjones]

Dave,

I sent you a PM... Hope to talk to you soon

Ken

[thehelix112]

I have to sort of disagree. To get a 1:1 ratio you're needing a pretty damn huge turbo. Certainly not something that'd be typically considered streetable. Do remember in the vid of zacs 1600 that we simply can't say acurately what the exhaust pressure was due to the fluctuations (100-200kPa). Even if you take the average of that you have a greater than 1:1 ratio.

I disagree. Looking at the vid, there is a significant amount of time that boost is 21psi and exhaust is constant at 14.7. As the flow/rpm goes up the exhaust pressure then fluctuates between 14.7 and 30psi. This is almost exactly 1:1 if you take the average, and only 1.5:1 when you take the absolute peak.

Streetable is up for consideration in the next point.

Totally disagree on this one. Firstly we should be clear on some terminology. When I'm refering to lag, I'm not talking about the the motor needing to be above a given rpm for the turbo to boost, I'm talking about how long it take to go from nothing to full boost when the engine is already at high enough rpm to spool the turbo. For example take an average turbo car driving down the road at 80kph, 2nd gear, 5000 rpm just holding that speed, turbo wont be boosting. Now floor it. How long does it take for the turbo to start making useable boost? That's lag!

No arguments regarding terminology (see I used both in my last post).

With pansy little turbos eg my mates VG30DETT, we're talking maybe 0.5 sec or so....not much. But when you're talking large turbos, we're talking seconds. Two good examples are two mates RB20 powered skylines, both with different large turbos. Both of them will take around 2seconds to start making useable boost.

Can't argue there.. sounds standard fare for a short stroke low displacement engine. 2 seconds is ridiculous if you are going by your previous indicated 5000rpm example.

That sort of lag shits me to tears. Sure the cars are fun being silly fast and all, but they're almost useless when it comes to the corners, because it simply wont make the power you want when you want it.

Example 1: Brake hard for the corner, even get hard on the power very early in the corner and it still wont make good power until you're out the other side.

Example 2: We were out in the middle of nowhere and decided to pull a donut.....drop it in 2nd, rev out to the limiter almost imediately, so back of the accelerator to get it off the limiter, foot down again, oh look its dropped off boost, then bogs down before it can build boost again.

Basically the same happens in corners. Sure it's an extreme example this car having a rather large turbo and all.....but the same happens with pretty much any turbo setup.

Errr.. not really. You just can't make a blanket statement about all turbo's like that. That is EXACTLY what frustrates me. How many turbocharged cars have you driven in anger? Have you been in one that was a decent quality build? If you are building a good quality turbocharged engine you take into account approximate boost threshold and ensure that the engine has a usable power band above this. If you have 2 seconds lag at 5000 (which to be honest I don't believe at all) the engine is already what? 6500-7000 in that time and just about out of revs. That makes it rather unusable, and not a good basis on which to judge every turbocharged car ever built.

BTW, what is this large turbo on the RB20 you speak of? I haven't been in too many turbo cars, and I've only driven one in moderate anger through corners (my L28 with GT35R) and its simply a non issue. At 3500 you simply feed the power on as you exit as per a normal engine. Obviously lag will never be zero so perhaps you start to feed it on slightly sooner than you would otherwise but its still perfectly drivable.

Having come from the 260Z where I am some what spoilt for throttle response, any amount of lag shits me to tears, even the tiny little bit in my mates Z32 tt.

Haha.. I personally don't understand peoples preoccupation with throttle response, as I said, the only drivers I can see who require it are rally drivers. If you're going round a circuit then you know exactly whats coming up and can select what gear is required to get lag down to an absolute minimum.

I will screenshot some of the datalogs of my turbo engine so you can see how long it takes to come on boost from different RPMS after you plant it. That should give us some points for discussion.

Dave

[thehelix112]

Yeah look what happens... we have a great conversation until you arrive with incorrect information and wrong quotes! Then try to turn a great thread into a turbo vs supercharger argument! Both a turbo and a supercharger have their place in the high performance world, it just depends on personal preference and the desired end result... Please don't continue along the lines that you started... it has no place here.

Ken, wow.

More points:

1. Cheers for the patronising.

2. I might point out that I wasn't the one to raise turbochargers, which I believe occurred on the 4th reply to the thread.

3. If I have posted wrong quotes and incorrect information, please feel free to point

them out to me. Everything I saw is for the purposes of education: I say something that I think, its discussed and if a valid argument against it is raised I then take that on board. I am not here to have a pissing competition.

4. I'll continue along the lines I started as I don't see anything wrong with them.

MANY people run more than 7 psi of boost with no intercooler for many reasons, from simplicity to cost to a whole host of other reasons. My supercharged 280z runs 13.5 psi on pump gas with NO detonation what-so-ever... MAT are monitored closely and have stayed within reason. While intercooling will help, this is an R&D project and I prefer to make small incremental changes so I can accurately analyze the results of EACH change.

Cool. I can understand the advantage of controlling variables and changing things one at a time. I also acknowledge that when you said boost levels in most cases wouldn't REQUIRE an intercooler is quite possibly true. If you are not doing it for R&D purposes though, I can't think of a good reason not to run one.

Did I ever say one dumps more air than the other? Ah No...

I was trying to understand what Datto-Zed was proposing and pointing out the challenges that he would face in tuning... I know this from experience based on my findings

Good point, I misread what you wrote on that one. Apologies.

I disagree... tuning around the bypass has been one of the biggest tuning challenges we have faced.

Well as I've never tuned a by-passed supercharger I won't comment further.

That is probably the most sensible paragraph that I've read from your posts... finally!!!

The only two points I'd made before this were in the first case, just a rehash of another's experiences that I thought might be of interest to some people, and in the second case, a very obvious observation about efficiency. Maybe if you hadn't taken offence you'd've seen that?

Well, sorry, but the whole depress pedal, wait, hold on, no wait I gotta grab a different gear thing isn't what I was looking for... Most people who are looking into supercharging are of the same opinion. While there are things you can do to reduce turbo lag (and let's not go there in this thread), reality is it can't be completely eliminated. My goals were to have good power that was there all the time. I didn't need to have a ridiculous amount, just good respectable power... I wanted to road race with my configuration (although its great on the street too). I wanted predictable throttle response through a turn on a road coarse with the power being there when I needed it. If I needed to feather in the throttle at the apex, I want the power to be there when I do so.

Fair enough. As I said, horses for courses. Though if you are doing what you said in the first bit of this you aren't exactly driving it well.

I've driven several turbo cars on the road coarse and they were all a handful to drive and as a result I was slower than when I drove a similar car with less power in a NA configuration ... why? because I was able to drive the NA much more smoothly.

I would say that any car takes a little while to adjust to, in my case at least. And I still believe its not that difficult to drive well above the RPM at which lag becomes absolutely minimal in a well setup turbocharged car

The merits of supercharging have their place in any performance application... that is reality. Quite frankly, if more people got a ride in my car, I'm sure it would make you reconsider several of your points...

The same could be said for turbocharging, and in having a ride in a proper turbocharged car.

This will be my last post on this thread... you guys have fun...

Why? We're just talking. Isn't the whole point to discuss things like this? Or have I `ruined' the nice little back-patting session you had going on?

Dave

[Murph]

Regarding my blanket statements about turbos, I did say that the examples were at the extreme end, but never the less, the same principles still apply (to a lesser extent).

As for the preoccupation with throttle response, I like it. It's totally irrelevant who you think needs it. I like it so I will choose engine configurations accordingly.

The car in the two second example was a RB20 NICS powered R31, using an HT18. Not a colossal turbo on the compressor side, but the exhaust side certainly is for a 2L. As per my example, 80kph, 2nd gear, floor it and it'd take around 2 seconds before it'd make decent boost. And no, it didn't run out of rev range.....before the turbo would spool it'd barely accelerate, it is a low comp 2L pushing 1500kg after all.

The second car in question and one I've driven in anger on many occasions is an R32 with an ITS turbo, not sure on the model but is said to be good for ~260rwkw. Better response than the R31 had, but still a pain in anything twisty. That extra .8L of a liter you have makes a BIG difference. You should line yourself up a drive of a small capacity, large turboed car some time and you'll see exactly what I'm talking about.

Haha.. I personally don't understand peoples preoccupation with throttle response, as I said, the only drivers I can see who require it are rally drivers. If you're going round a circuit then you know exactly whats coming up and can select what gear is required to get lag down to an absolute minimum.

This statement makes it quite obvious you're not quite grasping what Ken and I are talking about.

Ken summed it up perfectly with:

My goals were to have good power that was there all the time. I didn't need to have a ridiculous amount, just good respectable power... I wanted to road race with my configuration (although its great on the street too). I wanted predictable throttle response through a turn on a road coarse with the power being there when I needed it. If I needed to feather in the throttle at the apex, I want the power to be there when I do so.

[thehelix112]

I don't want a drive of a small capacity large/incorrectly turbo'd car that doesn't have the rev range to have a usable power band. The HT18 is a S5 RX7 turbocharger is it not? In which case the turbine housing is WAY too big for the RB20 (as you say) and is the reason its such a pig. $50 at a turbo place would've brought you a VG30DET housing which bolts on and solves that problem. Doesn't sound like fun to me. Noone likes lag, my point was that its not the unsolvable problem people make out. I'm still having trouble believing the two second lag @ 5000rpm thing. Maybe it felt like 2 seconds? Or do you have a datalog to prove otherwise?

Perhaps I'm not getting it entirely, or maybe its both of us, but my point was that in a well-setup turbo car power IS there when you want it. A turbo car only has lag while the turbine is accellerating, when it is up to an appropriate speed there is no torque rush, there is no lag, and throttle response is comparable to a N/A engine.

Have you ever driven your car long at moderate RPM, very light throttle and heard the BOV venting constantly? My engine does this at between 3500 and 4000. So lets be pessimistic and say its 4000, that means if I'm going round a corner at 4000 I have perfect throttle response, exactly the same as I would if I didn't have a turbo at all, and I can feather it all I want.

Of course turbo cars add another complication and this makes them harder to drive, but who doesn't love a challenge?

Dave

[chickenwafer]

Ken, have you comtomplated a centrafugal (spelling) supercharger? This would combine the best of both worlds, assuming it would work (I don't see why not...). And it would be smaller and more compact.

Food for thought- I saw in Road & Track (or MotorTrend, don't hold me to it) Jey Leno's Oldsmobile Tornado with a custom twin-turbo V-8. The twin air-to-air intercoolers were mounted pretty trick- inside the front wheel wells. You could possibly do that with your water-to-air intercooler? It would shorten intercooler piping and make the setup a little simpler and less cumbersome (i.e. pipes all over the place so you can't squeeze a wrench in-between them to get to anything). I don't know how well the air would flow into the wheel wells, but something tells me that if they can support a 1000-bhp+ monster motor then it would be ok. Possibly custom fenders with ducts to increase air flow???

What kind of fuel setup are you running? What size injectors and fuel pump? Just curious..... And, do you estimate with more boost (say close to 20 with a different SC), water-to-air intercooler, custom head work on the motor, a custom cam, stepped up fuel system, and other horsepower-goodies you could see more than 320 or so horsepower at the rear wheels??

I don't want to get into the turbo vs supercharger thing, but I will say I like boost more than no boost, no matter how I get that boost. The best compromise here is a hydracharger, but the inventor is failing to sell it to companies and he has a patent.

Thanks for the insight

Dave

[Murph]

I don't want a drive of a small capacity large/incorrectly turbo'd car that doesn't have the rev range to have a usable power band. The HT18 is a S5 RX7 turbocharger is it not? In which case the turbine housing is WAY too big for the RB20 (as you say) and is the reason its such a pig. $50 at a turbo place would've brought you a VG30DET housing which bolts on and solves that problem. Doesn't sound like fun to me. Noone likes lag, my point was that its not the unsolvable problem people make out. I'm still having trouble believing the two second lag @ 5000rpm thing. Maybe it felt like 2 seconds? Or do you have a datalog to prove otherwise?

Not everyone lives in your happy little world of larger capacity engines that can make big power AND still have a responsive turbo. I think you really need to go drive a 2L with a larger than stock turbo, then come back and comment. I'm quite aware the R31 didn't have an ideal setup, but I can guarantee you it was pretty near on 2 seconds. Unlike your large capacity engine, at that load condition the R31 wasn't producing anywhere near the exhaust flow required to spool the turbo.

Perhaps I'm not getting it entirely, or maybe its both of us, but my point was that in a well-setup turbo car power IS there when you want it. A turbo car only has lag while the turbine is accellerating, when it is up to an appropriate speed there is no torque rush, there is no lag, and throttle response is comparable to a N/A engine.

As before, go drive a 2L with a larger than stock turbo. It's not like they're uncommon.

Have you ever driven your car long at moderate RPM, very light throttle and heard the BOV venting constantly? My engine does this at between 3500 and 4000. So lets be pessimistic and say its 4000, that means if I'm going round a corner at 4000 I have perfect throttle response, exactly the same as I would if I didn't have a turbo at all, and I can feather it all I want.

Would you agree power output will change with boost pressure? Yes. Good. Say you're balancing it around the corner like you said. Say you squeeze the throttle open another 15%, does boost instantly change with and proportionally follow throttle position? No. Maybe close on your engine, but refer to response No. 1. You see, that's what you get out of an NA or supercharged car, that's what I personally want.

Of course turbo cars add another complication and this makes them harder to drive, but who doesn't love a challenge?

Is this an admission?

[Murph]

Chickenwafer: A centrifugal supercharger isn't the best of both worlds unfortunately. With them, boost pressure is proportional to engine revs. Basically this makes them no better than a NA engine down low, with less mid range than a turbo engine and can only match a turbo or twin screw supercharger on peak power.

What's this hydracharger? Never heard of it?