Twincharging - calling Warpspeed! 3

[madmac666]

thread71-174690

Hi guys, i subscribed to this forum because i found the thread (referenced above) on twincharging while doing a Google search for information on this subject.

I have to say, the thread and contributions from forum users was very good and informative, which gave me a direction to follow for my own twincharger build.

Some background on this: I have a 1997 Mitsubishi Lancer Evolution 5 which i've used for sprints and hillclimbs in Scotland for a few years now. The state of tune of the car is such that we were producing around 650hp, but with the big turbo at 2.6bar, lag was always an issue. Twincharging seemed the most sensible option for the car to eliminate the lag and hopefully produce a torque curve with spool much lower in the rev range.

I'm using a Harrop HTV 1320 blower and the existing turbo which is a hybrid T04Z with 0.82 housing. This is the turbo that gave us 650hp previously, but on a 0,63 housing. The system is compound compression with the turbo feeding the blower. The blower has a 75mm pulley and the crank 150mm pulley so a ratio of 2:1.

I have the blower mounted and all pipework finished and finally had her on the rolling road a few days ago. We saw some impressive torque figures but had to cut the session short due to belt slip on the blower pulley when the turbo reached 1.5bar. The system i have uses a 32mm toothed belt but the length of the belt seems to be an issue as it's stretching and allowing it to jump over the pulley when the turbo spools up. We also had issues with controlling the turbo boost and decided i need to install another wastegate to allow better control of the boost. I'll have that done by next week RR session so we have control of the turbo boost and can carry on mapping.

It seems the belt starts to jump when the turbo reaches 1.5bar and the drive simply cannot cope with the power needed to increase boost by a factor of 2. I have a larger pulley (100mm) which i'll be fitting over the weekend and hope the longer wrap around of the belt on the larger pulley and the reduction of the drive ratio should sort out the issue of the drive. If it doesn't then i have another modification i can do to run a shorter belt on the blower and split the ancilliaries onto 2 separate belts but i'd like to try this again with the reduction in drive frst before i go to the trouble of a re-design of the belt drive. Space is at a premium so 32mm is the widest i can go and still have a chassis leg...

We never went above 4000rpm. Despite this, we saw 460ft/lbs torque and 360hp at 4000 and 2.9bar which confirms there's definatley power to be made! Obvously slowing down the blower will mean the turbo will need to be producing more to reach our goal of 2.5bar total. The outlet temp of 80c from the turbo at 1.5bar was logged, which is about the limit of the blower seals. I hope to keep the turbo around 1.5 bar so the outlet temps don't fry the blower seals. The combined air then goes through a very good intercooler and reduces the final temps to 16c (this is Scotland remember....!) at the plenum.

I think we're almost there and hope to have it mapped on the larger pulley with the extra wastegate fitted for turbo control. Looking at the RR graphs and data we collected the other day, we monitored the pressure from the turbo and combined total and can clearly see a multiply of the turbo by the blower very close to 2:1 from 1800rpm to 4000rpm but we couldn't control the turbo and it looked like it would have carried on climbing which would have killed the engine or the blower.

Because the engine already had the big turbo and supporting mods to make good power, we hope to see some good figures once the issues are ironed out. The engine itself is built to produce 1000hp 'reliably'.

I would like to hear any views and comments on my findings so far. I had considered swapping the turbo and blower order to reduce the power needed to drive the turbo but i felt the extra restriction on the exhaust (because the turbo would be working harder than it used to) would likely end up making less power, as the exhaust back pressure would then be much higher. It would certainly reduce the power needed by the blower


Thanks for posting the useful information, it really was a huge help and if you have anything to add that could help us, i'm all ears!

Donald

 

[Warpspeed]

I'm considering building a spaceframe Evo and use Skyline running gear mated to this engine and twincharger, but that's a huge project that i can't afford to do yet.

The GTR drive train is not without it's quirks.
The front diff is located in the GTR sump, and is pretty much impossible to adapt to something else (I have attempted this myself) and the available diff gear ratios are limited.
The front prop shaft is also on the same side as you, and the steering, which could get rather crowded in a race car. Much better to have the front diff and prop shaft over on the passenger side. Safer too.

But worse, the GTR's computer controlled wet clutch system that drives the front diff will have some very different characteristics to the much more benign and predictable epicyclic torque splitter you have in the EVO.

How the power is split in the transfer case is critical to vehicle dynamics and handling, and a major design decision that is going to be very difficult to change later on.

Start with a nice beefy epicyclic transfer case, and build everything else around that IMHO.

 

[madmac666]

I know of one person who has successfully mated the GTR driveline to the 4G63 engine although i have not seen any photos of how it was achieved. This is the sort of challenge i thrive on but i'm aware it's too big a project for me at the moment due to the cost mainly. The GTR is uppermost in my mind because it's relatively cheap to buy a complete donor car and the driveline is actually pretty strong as standard - stronger than the Evo driveline. It may be that i end up with it mid-engined in the spaceframe so would need to consider a totally different drive layout then. There are a few interesting 4wd gearbox configurations avilable at some pretty serious money so i'll be looking at all aspects of the build before i start any spaceframe project!

One of the biggest considerations is, do i want to move from the Modified Production Division into Sports Libre and be competing directly against single seaters! At the moment the Evo is regularly beating a lot of the single seaters as it is so my point has been proven with the car in it's current guise.

I'll certainly be enjoying her for a few more seasons as she is so any spaceframe project is a few years from beginning.

Here's some of the last videos from the season

Harewood:

http://www.youtube.com/watch?v=hYjdxjzMsgM&list=UUb-2LlrEb3dddOaBuoRsKUA&index=8&feature=plcp

Fintray 2nd FTD yet backing off before the finish line as the right kink when the car goes light at 80mph is a known car killer after the line!

http://www.youtube.com/watch?v=7d6cJP0p6t0&list=UUb-2LlrEb3dddOaBuoRsKUA&index=6&feature=plcp

Forrestburn NCR and division win:

http://www.youtube.com/watch?v=UIGGajhZuo0&list=UUb-2LlrEb3dddOaBuoRsKUA&index=4&feature=plcp

Loton Park (final round of the season):

http://www.youtube.com/watch?v=zXaqfePabNU&list=UUb-2LlrEb3dddOaBuoRsKUA&index=2&feature=plcp

Loton park in-car:

http://www.youtube.com/watch?v=8oqlPgeNgu0&list=UUb-2LlrEb3dddOaBuoRsKUA&index=1&feature=plcp

Here's an interesting video of the underbody aero in the wet. Not at any big speeds (max 70mph) but it shows a definate 'rooster tail' behind the car with the wing and venturi working:

http://www.youtube.com/watch?v=Vdm553FIuEc&list=UUb-2LlrEb3dddOaBuoRsKUA&index=3&feature=plcp

Will update with any news as it happens. I've been considering changing to a GT42 turbo as the power is now restricted due to the flow capabilities of the To4z hybrid and would expect to see over 1000hp on 98RON pump fuel using a GT42 unit. I'm confident the Harrop SC will deal with the extra flow so that is a natural progression to the project. The only unknown would be whether turbo lag may start coming back into the equation with a compressor that big.