daniel951

A guy here in colorado supercharged and turbo charged his evo and was making alot of horsepower. Imagine all that power in a AWD car

fast951

After the first few messages on page 1, I stopped reading. Few emailed to learn more about the turbo.. If my message on page 1 was not a clue, let me clarify it here.

There are no plans to stop producting the S2 or S3 turbos. The turbo ST is referring to is a prototype that derived from a totally different project. There are no plans to bring the protitype to life, as it's cost prohibitive (and of course we do not have the test results).

All along I wanted ST to have a better mid-range even at the cost of lower top end performance. I am toying around with a turbo (not for the 951!). I wanted ST to try it on his 951 for few reasons:
- He has a good log of what mod did what.
- He has a history on the "same" dyno.
- He can replace a turbo faster than any person I know of LOL.

Due to certain mods on ST's car, S3 turbo makes 1 bar boost around 3450-3500RPM. Prior, it made 1 bar boost around 3100-3250rpm.

My target is to lower spoolup by 300-500rpm, which will help mid-range torque as well.. Another goal is to keep the top end in the same range as it is now. The 600rwhp is STs long term goal and will not be a terget goal for this test.

There are no plans to bring such a prototype turbo to market. Today's VR turbos are custom enough, and not off-the-shelf items. The turbo we plan on testing will be a prototype, that's it. As of now, I do not have a date as to when the turbo will be ready for testing.

ST does not work for Vitesse, we are friends and he is a customer. He loves to keep modifying things, he kindly agreed to test for us (more like a test case to compare technologies, the test bed is the 951). I have an idea what the outcome will be. Till we test, it's nothing but an educated guess on my part.

toddk911

Well a supercharged 944 turbo would certainly eliminate any lag issues

A SC running 8-10 psi, if that, and then a nice big, "laggy" turbo to handle the high end flows; about 20psi. So the best of both worlds, but at a great deal of cost??

But that setup would allow for a solid power band from idle top redline!!

toddk911

John:

You think with your experience/knowledge base and now maybe some money that you have made you would run/back a 951 in a serious Grand Am/Rolex series realm???

Even the lowest/GT3 classes??

fast951

No!

Trucho-951

Don't forget to throw variable cam timing into to this wonderful stew...

special tool

HAHAH - John is currently the only person in the world who can control variocam plus on a vehicle/dme originally equipped with only variocam.







-no, he can't do it - try again




-neither can that knucklehead - call them and ask, if you don't believe me.

streckfu's

Do you mean AMAF?

theedge

Ive been researching it (twincharging). Theres several big hurdles.

First off is the supercharger itself. My very rough measurements indicate one that could fit. Its advantages is that it actually has no stupid long snout like most do, and it has a clutched pulley like whats on aircon compressors. The lack of snout means its less than a foot long (about 11.5" inches to be exact) versus 13, 14, 15 for snouted models. This makes it much more likely to be able to fit it in there, and use the alternator belt to drive it since those ACs use a 6 ribbed belt like our Alts. This also solves the tensioner issue, we just use the alternator rod. This all assumes that the pulley sizes work out, the tension needed doesnt kill alts and their tension rods, etc. If that doesnt work out, there is room for a second pulley and belt in front of the alts.

Next up, inlets and outlets. This could be a fairly minor issue though... To pack a supercharger in the old alternator location also looks like itll mean deleting the turbo water cooling OR rerouting things and ditching the crossover hardpipe, instead replacing with hoses since the outlet for the SC is going to be in that general area. The inlet on that SC is on the back, so a hose has to be routed to there. Might be a tight fit with the engine mount arm. Air source could also be tricky, but im thinking that the alternator cooling pipe might be a nice source of cool air, just stick a cone on the other end Outlet can be "merged" with the turbo outlet pipe going to the intercooler, or simply with the pipe FROM the IC going to the TB. This of course assumes a MAP equiped car, otherwise were getting into cramming a Y pipe in after a MAF.

Now, the biggest issue IMHO. The biggest bring down of Twincharged setups is getting the "crossover" point correct. At some point the turbo is going to be putting out more pressure than the SC, which will get ugly. With a clutch, we can simply turn it off at some arbitrary point (for MegaSquirted cars like mine, that can be based on RPM, MAP, TPS, or even a combo IIRC). That still leaves the issue of turning it off at the right time, and preventing air going back through it. Right time will be trial and error probably. Preventing backflow seems to get solved several ways, ive heard of several people just using big one way flapper valves.

Now what im unsure of is if the throttle body MUST go before the supercharger, or if it can stay where it is. The setup im thinking of is a full blown Y setup, rather than what seems to be more conventional with supercharger into turbo into engine, or turbo into supercharger into engine. This will take some more figuring.

The benefit of Twincharging is the choices in turbos you get after the fact. With the SC doing its part, theres more exhaust early to spool a monsterous turbo. In that pic posted of the Evo, the turbo is a Holset 55(?) that can flow enough for 1000+ Horsepower even at his colorado altitude. Without the SC he made a few PSI at redline

My research shall continue and id like to give it a try at some point, just because. I dont know when though.

lart951

It was a supercharged twin turbo setup, lol.

pk951

Do you guys remember Bob Howard. This car was featured in the April 2003 Excellence Magazine. They had the turbo sitting were the windsheald water tank is, that would make for a fast spooling turbo, right from the headers to the turbo. Has anybody tried that set up, other than Bob Howard on his car.

Trucho-951

If you really are seriously thinking about giving it a try, here is a quick blirb on how Mazda engineers approached their design...

"How are the turbos configured?


The 3rd generation Mazda RX-7 has the world's first production twin sequential turbocharged engine. The key word here is sequential. In every other automotive twin turbo setup, the turbos provide boost simultaneously. Each of the turbochargers in this type of application is generally smaller than the one turbo used in a single turbo setup. A small turbo accelerates quicker, suffering less from "turbo lag" than its larger counterpart and, as a result, produces less power and torque but sooner and at lower rpm. Fitting twin turbochargers in sequence produces better results as the first turbocharger receives the full force of all the exhaust gasses (instead of sharing with the other small turbo) and gains speed much quicker, which enhances throttle response and increases low speed torque. At a predetermined speed, the second turbocharger is called upon to add more boost. With the twin turbos in full operation, exhaust gas flow resistance is greatly reduced, contributing to higher power output.

Assuring a smooth transition from single to twin-turbo operation as been an inherent problem with the implementation of a sequential turbo system. If the secondary turbo is not spinning at a high enough speed when it is brought in, the whole system "staggers", temporarily failing to produce enough torque for a smooth change-over.

Mazda's rotary engineers attacked this problem with a vengeance and perfected a solution to this technical challenge. In the primary boost stage, when only the primary turbocharger is operating, a portion of the exhaust gas is led to the secondary turbocharger, spinning it into a "pre-operation" mode. The boosted air from the secondary turbo is not required at this stage, so it circulates in an essentially closed intake chamber. Left in this condition, the turbo would eventually go into what is called "surge". This phenomenon is accompanied by a rapid temperature rise at the entry and exit of the compressor, which would harm the turbocharger if prolonged. In order to preclude this surging condition, a bypass valve is opened to form a loop in which the air circulates.

The secondary turbo maintains a pre-operation speed of around 100,000 rpm. However, this is still not high enough to effect a smooth transition to twin-turbo operation. The secondary turbocharger must accelerate faster. This is achieved by deliberately inducing surging by closing the bypass valve and letting the compressor spin within a closed chamber. This sends the secondary turbo's speed to as high as 140,000 rpm. When this speed is attained, the secondary turbocharger receives its full share of exhaust gas, and, at the same time, a control valve opens, allowing the secondary turbocharger to start supplying boosted air, adding to the primary turbocharger's. As previously stated, surging is harmful if prolonged, but in this transition state, it only lasts a few seconds, and therefore has not detrimental effect on the engine's durability and reliability.

The RX-7's 13B engine used twin Hitachi HT12 turbos with a 51 mm, 9 blade turbine and a 57 mm, 10 blade compressor. The turbine and compressor blades are a curved "high-flow" type that offers less resistance to air and gas flow. This results in faster turbine and compressor spin-up at high rpm.

The twin turbos are mounted on a cast iron exhaust manifold which has been named "Dynamic-Pressure" manifold by Mazda's rotary engineers. This manifold is elaborately shaped to minimize the distance between the exhaust ports and the turbochargers' entry paths, improving low speed boost by as much as 25 percent."

theedge

Good info, but im not talking about twin turbochargers, im talking about twinCHARGING, where a supercharger and a turbocharger are used on the same engine.

IanS

Not many people have done it outside of a few race cars. I have to think it would be cheaper than the SFR stage 2 headers at $2k. The cheapest option would probably be to use the stock headers, then go directly into a turbo where they merge together down below, but that may not be high enough for good oil flow. On the positive side, you could use a dual-scroll turbo.

95Juan

mini coopers and Toyota MR2's with camry motors love this approach.