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I've been looking at building a pump gas 2JZ for a while (I've had the car for 24 years). I had been on the assumption that something around 600hp, maybe 650 was going to be the max.
Then in response to a post about displacement on a Supra forum some posted the 892 number with the graph below. The other line is E85. The engine was 3L, 10:1, with a big 7675 turbo, GSC S2 cams (about 240°@1mm), ported head.
Originally I was thinking of an EFR 8374 or 9174 with the S1 cam (about 230°@1mm) and OEM level 8.5:1. Now I'm thinking that isn't enough. However, I thought a 74mm titanium aluminide turbine was heavy...an 82mm Inconel doesn't seem a step in the right direction. The big cam maybe gave room for the big cam. That would need VVTi IMHO to make it livable. At least GSC has an new R2 cam with an extra mm of lift.
Does this much power from a streetable pump gas engine seem right? Or am I chasing after ghosts?
Ok so a few things to think about here. First of all it's easy to become mislead by what others are doing and start heading down the path of 'more is better'. For a drag application that may hold up, but it might not be the best for a street car or a circuit car. Power delivery is every bit as important as the peak number - Often more so.
Next up is that you need to be mindful of comparing dyno figures. The one you've posted is off a Dynojet which is almost an industry-standard in the US but still reads very optimistic compared to the likes of a Mustang, Mainline or Dyno Dynamics. As an example I use a factor of about 1.18 to convert our Mainline values to something you'd see on a Dynojet so that 892 whp on the DJ is going to be closer to 750-760 on a ML. Just make sure you're comparing apples with apples to avoid disappointment.
Personally if I was aiming for big power from pump gas with a 2JZ I'd be sticking to a compression ratio of around 8.5:1 or maybe 9:1. 10:1 is more suited to E85 or race gas and you're almost certainly going to be knock limited at high boost on pump gas. You'll also need a bigger turbo than the 8374 to do it. The 8374 is a 79 lb/min compressor wheel which on pump gas is probably going to limit you to maybe 650-700 whp. Stepping up to something like the 9174 or 9180 will probably get you closer to 800 whp but I doubt you'd get as far as 900. The 7675 is a 1200 hp turbo so it's quite the jump up from a 8374 or 9174.
Really only you will be able to decide on the compromise you want. Even 650-700 whp will make for a very exciting ride though and with an EFR turbo on board the lag will be minimal and the power band will be wide.
We build and tune a lot of 2JZs in my shop, but a 10:1 setup is always most exclusively an E85 or race gas engine. As Andre mentioned 9:1 is probably the highest we'd suggest for pump gas use, and even then we'd build this for the German 102octane ROZ pump gas, which contains about 10-15% bioethanol.
With that fuel we can almost always run a couple more degrees of timing and boost pressures over 30psi, than with our regular 100octane ROZ before experience any knock.
On a lower grade fuel, 8.5:1 is something to consider.
I guess, what I'm trying to say is, that I have a hard time believing those 892whp on pump gas in comparison to 965whp on E85. That jump seems a bit low compared to what I've been seeing even with the same boost pressure. Also this dynorun might just have been a single run, and boost/timing isn't something the owner is running on a daily basis.
Look, most dynographs in forums are misleading people into what they could achive with a given combination of parts, because most likely the poster would like to impress everyone (that beeing said, there are also some honest people out there ;) ), so talk it with a grain of salt.
If you want a fun ride on the streets with good boost response and power, I'd look into building a 700whp setup. More than fun and if you wish, get your groceries in that ride ;)
Thanks for your input! I tend to agree. I've been trying to get more info. Tuned for E85 that engine has made over 1100hp and temps were 65F on the test day. Cooler air is just like more boost in creating a denser charge and I suspect leads to higher chamber pressures with lower chamber temps.
On the surface, it appears the big question is how 22psi at 10:1 compression avoided detonation on pump gas. 22psi should have been pushing it even at OEM 8.5:1 compression. The answer may be in some Atkinson cycle like reduction in the compression ratio while maintaining the higher expansion ratio and maybe increased swirl with the flat top piston. Getting more information on the dyno run may also be revealing.
Originally I was just thinking of replacing the OEM maze with a single EFR 7163 using the Garage Whifbiz OEM replacement side mount intercooler and a replacement ECU.
There was pushback from both sides. On one hand, it was I keep my original owner 70k Supra original, or if anything use the Stu Hagen upgrades which are largely hidden.
The other was that the small turbo was useless on the 2JZ...and it should be bigger. As I understand it, the 2JZ has too rev limitations: oil pump and breathing. Ported OEM oil pumps appear good for 8500rpm. A dry sump, always my preference, is hard to fit on the Supra while keeping the power steering and A/C.
Breathing would mean a ported head with the GSC R2 cam and probably VVTi to keep everything drivable. A prepped bottom end would be a stroker, with the big questions being around how much stroke, piston compression height, rod length, rod BE and PE diameter, ring stack, etc. The power levels may be too big for any single EFR, requiring a dual turbo setup.
The question is for what purpose? We live in an era where mainstream 4-door sedans are quicker in acceleration and higher in top speed than the muscle cars of the 1960s. Sports cars have more power than actual race cars in the premier racing series. Meanwhile, actual amateur racing becomes rarer (even the drag strip near me closed) and road courses are more like golf courses focusing on 'track days' with memberships, clubhouses, etc.
Honestly, we cannot answer the question why the guy on the forums was able to run 22 psi on a 10:1 2JZ with pump gas, there's just too many variables why this was possible. Maybe there wasn't just 93 in the tank... but whatever... don't focus on that.
More importantly, make up your mind which route you want to go, as you've just brought food to the table for a discussion as to why we need faster and more powerful cars ;)
Short answer, we just need them, period.
It sounds to me like you're unsure of what your goals are. You might be able to narrow things down by thinking about what sort of events you might use the car in, and how much power it might take to compete at the level you want to run. I'd also try to get a ride in as many Supras as possible, especially cars making 500, 600, 700 hp. I would keep all the parts to go back to stock, in case you change your mind later.
First, I agree with Andre about being careful comparing dyno numbers. You don't know if that dyno has been maintained and calibrated recently for example. A few engine related comments:
1) The later the intake valve closing timing, the lower the effective compression ratio (Miller/Atkinson Cycle). A perfect example of that is the Fiat/Alfa Romeo/Chrysler/Jaguar MultiAir/UniAir system which runs late intake valve closing under boost.
2) The larger the turbine housing, the lower the residual gas and the lower the pumping losses. Less residual gases reduces the knock. Also, monoscroll is better for residual gas and top end than twin scroll (not sure if this guy was using monoscroll).
3) You would probably enjoy the car more by swapping to VVTi head and keeping everything else. You'll get more low end and spool by being able to dial in overlap and run earlier intake valve closing timing at low rpm. Remember, the modern version of the 2JZ engine is a BMW straight 6 (N54/N55/S55). An S55 is twin parallel turbo direct injection with cam phasing possible on both intake and exhaust (also valve lift but that's not so important at WOT on Valvetronic, it's different than a Fiat MultiAir system).