In Part 2 of our interview, we speak to a leading industry expert Simon Gishus about Nissan engines, Holden Gen 3 V8s, and directions for modifications...
What are some areas where people often make errors modifying their turbo car?
"The classic blow-off valve.
"The blow-off valve is designed as an emissions control device for OE manufacturers. It came about when smaller engines made more and more power using larger turbochargers and bigger intercoolers. As you close the throttle, the build up of pressure and the larger volume inside the intake has to go somewhere; it can't go into the engine because the throttle is shut. Instead, it has to do a U-turn and it comes screaming out the airflow meter. That creates the 'gobble-goggle' sound.
"The gobble-gobble sound is something the public has grown to love.
"The airflow meter is not all that smart and does not realise the air is going in the wrong direction; it therefore measures the air twice (once going into the engine and again going out in the wrong direction). The computer now tips in twice as much fuel as what's required, making it run rich - making it not pass emissions.
"Therefore, manufacturers fit a blow-off valve - or a recirculation valve as they are actually called. A recirculation valve opens when it senses manifold vacuum, returning the air trapped at the throttle body to between the airflow meter and the turbocharger. As such, the airflow meter does not take a double reading - the car now passes emissions.
"Unfortunately, we've had people ringing up and wanting the "audible gear change alarm".
""What audible gear change alarm?" we ask. "You know, when the Sierras were running around and just when they went to change gear it used to go whoda-whoda-whoda" they tell us.
""No pal, that is the dump valve..."
"Some people do think that at the absolute upper extremes of boost levels - about 30-plus pounds - the blow-off valve does, somewhat, save the compressor wheel and shaft from trying to rotate backwards. It doesn't actually rotate backwards at all - all you're hearing is cavitation. What happens is, you've shut the throttle, the turbocharger is doing 100,000 rpm and now has a boost spike of 50 psi. Because it's working in a higher region than what it's designed for, it slips; it basically does a skid like a car tyre does when you dump the clutch. That's the noise you hear - the whoof-whoof-whoof is the air doing a skid."
Is there any performance gain to a blow-off valve?
"We've tested one on a manual gearbox performance car run at Winton Raceway. I think it was running 1 minute 40s back then, but it would lose 2 seconds a lap putting the gobble-gobble valve on. When you look at data acquisition, what you find is - as you change gear - the blow-off valve dumps all the pressure built up through the intercooler and pipes. It then goes back to zero manifold vacuum when you get back on the throttle, you have to build all that boost back up.
"The fact that people think that they keep the turbo spinning is a problem. The people that suggest this have never had an engine on the dyno and never had a turbo tacho in their hands. What people don't realise is, when you shut off the throttle, you shut off the air supply to the engine - this shuts off the exhaust gasses coming out of the engine. When there is no exhaust flow, there is no energy to keep the turbine spinning - the turbo slows down at an alarming rate.
"If you change gears at quite a good speed, you can actually get a boost spike on changes; if you're trying to hold a constant 30 pounds, when you do a racing change you'll get 32-33 pounds when you crack the throttle open again. If everything's working well, you've got a full head of stream waiting to go into the throttle as soon as it's opened.
"I've done this on a rally car and it was quicker through every timed section without a dump valve. You'll never hear a World Rally Car going pssshhht because they don't use a dump valve - you get the woof-woof-woof noise instead."
What are your views on custom modified 'high flow' turbos?
"I've sort of gone away from that now - I typically buy what's off the Garrett shelf. Anyone that thinks little Simon in Bayswater is going to be smarter and have a bigger development program than Garrett is kidding themselves. They do make very good things available straight off the shelf, so long as you know what to ask for. We've come up with a bit of a formula of what we need for each different car.
"Because nobody's got good data acquisition or good turbo tachos, the modifiers often put incorrect things together, overspin the turbocharger and explode the compressor wheel. At that type of speed they go into the surge range then they f?*^ their thrust area. They can also stretch the back of the turbine wheel blades when they get very hot, and then there's the question of whether or not it's got a left-hand thread exhaust wheel."
How do you decide on the appropriate size for a turbo?
"As I said, everything we do now is basically to a formula - we've done the R&D and lots of testing. If you want a 400, 500, 600, 700, 800hp [Nissan] RB30 we know what it is - we go back and look at what we've used in the past. We get good correlation of data and we do lots of data acquisition."
Moving onto your current engine of focus, what progression of mods do you suggest for the 225-255kW LS1?
"Obviously, our kit...!
"In most instances, the biggest problem comes from the engine management system - it's very intelligent. Modify the car in any way and the system half trims itself back to whatever the original power was. Whack an exhaust on, whack extractors on and do all that stuff - but, if you've got the standard management system, whatever gains you make you'll lose at least 50 percent over a period of time - depending how you drive it.
"You can make your extra 25-30kW, but give it two or three weeks of hard driving, whack it back on the dyno and it'll be only 6 or 7kW better than standard - and it's going to be noisier. Unfortunately, an aftermarket engine management system almost has to come if you're serious about doing it. To get to the bottom line, any of those LS1s with an airflow meter limit you to about 262kW at the engine. You can go for a bigger airflow meter, but - to my knowledge - there's no way of telling the computer that."
And how does the HSV 300kW engine respond to mods?
"The 300kW engine is actually a pretty good piece of gear. With exhaust modifications - using the HSV extractors - and a new management system we've seen 319kW out of them on the engine dyno. Again, we've got to make sure we use all the same ruler, though. We've had guys come in with a rampod and an exhaust on their GTS and they've got 340kW all of a sudden..."
What are your views on the well-documented LS1 engine failures?
"They definitely have got an oil consumption problem. It, no doubt, gets back to the low friction rings they're using to try to achieve good mileage. I think it's probably also very important how you run them in and what oil you use.
"All of the oil pressure problems come back to the fact they have oil change intervals at 10,000 kays. By 7000 kays you've got an engine that's probably used a litre-and-a-half of oil, you tramp it off a set of lights and it pulls the oil pressure light on. If you thrash the guts out of it at that point it will, yes, throw itself to pieces.
"Everyone is shitting themselves that the conrods are going to fall to pieces. They're a sintered metal conrod, which are probably very good in compression (for example with nitrous oxide or a turbocharger). I don't think you'll have problems with them for a very long time. My guess is that they're not that good under high rpm - I think the rod's grain structure is not that way inclined.
"But, look, our test tune engine pulls 6250 rpm, it's done 250 ramp tests - well, actually multiply that by three because we do three tests up and three tests back for the average. So there's 750 dyno tests after we've tuned it...
"About a month back we did a lot of camshaft profile work and we put 600 litres of fuel through it in 3 weeks. It never goes for a cruise down the road - it's a thrash engine... and it's still all in there.
"I don't run a rev limiter on the dyno because the dyno grabs it with the electronic throttle, but we did have an incident where one of the water lines came off the retarder and the thing buzzed to probably 8500 rpm before it went "holy shit, get off it"; and the engine's still all intact.
"As I said, it's half a good thing.
"At the end of the day, our Stage One kit is making 221kW at the wheels and it still gives up to 40 miles per [imperial] gallon and passes emissions tests. Then there's the Stage 2. For the average punter that's going to buy a SS Commodore and spend 10 grand on it, he can have a 330-plus kilowatt car that he can still let his missus drive it with no special instructions. It's a pretty good thing - a 450hp-plus road car.
"I'm one of those 2-litre turbo guys, but - look - my ute with the Stage 1 will trounce a standard WRX, Pulsar GTi-R and it'll pull away from Vinnie from BGT's 200SX with its 155kW at the wheels. It's similar money too - about 6 or 8 grand."
Mechanically, what are the limitations of the standard LS1?
"All the typical things become a problem. The 225-255kW camshaft, by the time you hit where we're at with our Stage One kit (at about 285kW), it cannot breathe any more."
What is your favourite aftermarket management system?
"MoTeC. The two best ones in this country by absolute streets are MoTeC and Autronic."
And what's your opinion of interceptors?
"Well, everything has its market - I don't know much about them. The software's not readily available and I've never tuned one. I'm probably not the right guy to be asking. I'm told there are 12 adjustable points - all the rest is left to the factory. It's really hard to say though - even with the best system in the world, if it's not tuned right, it'll be no good."
Why does your workshop have both a Dynolog chassis dyno and an engine dyno?
"You can't do serious research and development on a chassis dyno - end of story.
"You can't hold long power runs on a chassis dyno - the car won't support it. The radiator, oil cooler, intercooler and everything won't cope with 220kW for 5 minutes at a time - it'd just turn to moosh. Generally speaking, the chassis dyno itself won't cop that either - they have an electric brake and they just glow red. That is fundamentally the main reason - to do thorough research and development, you need an engine dyno.
"We do all of our big projects on the engine dyno - you can pull camshafts in and out easy, as well as turbos and all that stuff. You can do cold starts easier as well.
"If you're going to do tuning, you can absolutely get away with a chassis dyno. The majority of our tune-ups are done on the chassis dyno - you can get them probably 85 percent, maybe 90. Anything that's drag oriented with a big converter in it, though, you're kidding yourself if you try doing it on a chassis dyno. You can never get to all the load sites."
What difference in measured power do you see between the engine dyno and the chassis dyno?
"We've only just installed the Dynolog chassis dyno, but - generally - we've seen a 26 percent loss in rear-wheel-drives. Front-wheel-drives should be the same, so long as you tie them on properly. Our dyno runs a very large diameter wheel and so it gives very good grip."
So you see the same percentage loss regardless of a front-wheel-drive or rear-wheel-drive layout?
"Yes - it's the same between a Nissan Patrol and a NX Coupe.
"Look, there's a 3-hour debate on where the power gets lost. Do I think that 26 percent of the power is lost through the gearbox and the diff? Absolutely not. Sheer mathematics will tell you that, if you've got a 400hp engine and there's 26 percent lost through the driveline that's 100hp. Every bit of that horsepower is heat; if we've got 100hp being absorbed into the relatively limited volume of oil in the gearbox and diff, it'd boil that oil in minutes. I know that they do dissipate heat, but - if we leave that out for the moment because it's very complex - the fact that the oil doesn't boil says that theory's not right.
"Very shortly we're planning on using an infrared laser light so we can measure the speed of the wheel and the speed of the roller on the chassis dyno. That way you can see the slip - and there will be slip, no matter how well you tie a car on. We can also stick a load sensor on the engine mount so we can see how much torque the engine's got. Then we can say, "Well, the engine's doing this amount of rpm and with this much amount of torque through the engine mount."
"It's one of those things that I want to do that interests me for my own sake, rather than anything else.
"I think there's more like probably 8-10hp-ish lost - whatever percentage that works out to be - through the gearbox and probably another 5-7hp though the diff. The rest is then slip between tyre and roller, the wind generated off the tyre, off the rollers and off the big finned brake on the retarder. There's a lot in that, because they make exercise bikes these days that have nothing else but flaps that you've got to try to spin through the air - that draws power."
What would you say are the best five products currently in the aftermarket?
"MoTeC, Carillo conrods, Del-West titanium valves and some of the Crower internal type engine stuff. A lot of the Japanese stuff that comes over - like A'PEXi - is also unbelievably made. It's magic - it comes in better packaging than an $8000 television set."
What do you predict might be the biggest breakthroughs in the aftermarket over the next 5 years?
"I don't think there's going to be any huge breakthroughs. I'll think we'll see a steady progression as the general public and the workshops get right up with technology.
"We're running 12-seconds in Gen 3s now and, in 2 years time, we'll be able to run 10s - of course, there'll be that huge increase in power. World records will tumble and cars will go faster, but that's where I think it'll all head."
Do you think electronic throttle control might be useful?
"Yeah, that will be good - MoTeC are doing fly-by-wire.
"There are times when you've got a naturally aspirated engine that's got big ports, big runners and all the stuff - at full throttle at 3000 revs it might make less power than 50 percent throttle at the same revs. So to have a system where you go full throttle - but it looks at 3000 revs and only gives you 50 percent throttle - is a really good breakthrough."
Is there anything else you'd like to add in regard to vehicle modification as a whole?
"My catchphrase at the moment is, "there is no magic".
"When people say they're making 500 horsepower out of a 5-litre engine and they're only doing 6500 revs and they've only got 'X' compression ratio and 'X' fuel, you can quickly work out whether it's bullshit or not.
"Yes, we'll be making more power out of a Gen 3. Are we going to then detrimentally affect its fuel economy, drivability and emissions level?
"There is no magic. Unless they bring out variable cam timing or BMW give Chevrolet and Holden their new electro-magnetic valve operation, there ain't no magic.
"It's all about compromise.
"Even our 330kW package I haven't rushed to fit it to my ute, because I am so happy with how it goes with 285. It's absolutely so tractable, and - really -you spend so little time between 5000 and 6500 rpm. Bloody hell, I've run it up a couple of times today [on the chassis dyno] to give you guys a power figure, but I haven't been up there for a month and a half. I just tool around - unless I'm racing Vin or someone!
"I love the fact it does 40 mpg on a trip, and it starts, idles and does all that beautifully. Every Gen 3 I've come up against on the road has been absolutely torched - so why bother? I gave a GTi-R Pulsar a run the other day and absolutely annihilated him.
"Ten years ago when I was 25, she would've had her 333 and had gas on it and been tearing up the road doing skids. I've got over that a bit - I've got a race car and I've got a road car. As we said, you can't have both in the one car..."
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