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

 

[madmac666]

I agree with Warpspeed on this. When my bypass worked, it worked faultlessley. The control of the bypass done with hoses taking pressure or vacuum signals is so simple and directly related to actual engine/boost and throttle conditions.

I have never even considered using electronics to control this part of the system due to the complexity of setting up the software - let alone building it in the first place.

On another note, i just had my mapper on the phone saying a coil has packed in and he can't continue the mapping. We have a set of Hyperdynamics coils available to use but i suspect i need to look at a better system now. I had hoped this could wait until the engine was rebuilt but now it seems the tuning gods have spoken and are telling me to get it upgraded now...

 

[madmac666]

Mapping finished, dyno results here:

http://www.flickr.com/photos/39729338@N07/5449266792/

Am pretty pleased with the results! We seem to have lost some torque since the last dyno session although it was a different rolling road last time that only measured wheel power.

The mapper had to gently squeeze the throttle at 1800rpm to stop the car trying to launch off the rollers, so the bottom end of the map isn't at full throttle.

Now finally i can get the tired engine out and rebuilt! I will be changing the cylinder head and cams at the same time so i reckon there's more to come before the season starts.

Can't wait to drive it hehe

 

[70btdc]

Why are the two traces not crossing at 5252rpm?

 

[dgallup]

Because they have different vertical scales.

 

[madmac666]

Saw that and queried it with my mapper - the scales are different so each line is to be viewed as though it is on a separate graph.

Update, the engine is out and in component form, showing little signs of the hard work it's done for the last 4 years. The pistons and bores are just on their tolerance limits so i've decided to go for a rebore. It's away for a new crank and 86mm pistons, oil pump and seals as well. The rods have been crack tested and are good to re-use. They are rated to 1400hp. The intention is to build the engine to withstand (and hopefully eventually produce) 1000hp reliably. The cylinder head is being ported to suit the induction setup, with higher lift & slightly shorter duration cams with solid lifters.

Could get interesting....!

 

[Warpspeed]

I just hope the drive train can cope with this.
Big torque and four wheel drive can be pretty hard on the clutch and transmission. Metal fatigue is going to be your worst enemy.

 

[madmac666]

All the transmission breakages so far have been down to fatigue, so i'm 'lifing' components now. I stripped first gear on launch last year and realised this gear had done over 500 launches before it broke! The only other part that has failed was the hollow output shaft from the gearbox to the transfer box. I replaced this with a Ricardo shaft which is a much stronger material than the original one.

Very aware that the drivetrain is the weak point now!

I always load the drivetrain before launch and don't just drop the clutch to avoid the sudden impact through the components. That method has served me well over the years but with this new power and torque, i have concerns! The flatshift is also kinder to the dogbox as opposed to using the clutch to change gear.

I guess i will have to beef up areas of failure as they happen to eventually iron out the weak points. This had to be done with the clutch and i've ended up with a triple-plate 'superclutch' that is showing little signs of wear after 4 events

 

[madmac666]

Update:

The new engine was built, mapped and we started the hillclimb season in April. A few transmission failures have hampered the reliability and although not unexpected, these have been quite costly and stopped me developing the car further. So far the results have been a new class record at Prescott Hillclimb, a 2nd FTD at Fintray and some good times at other events. The weather here has been terrible so most events have been wet/damp and records have been unachievable!

I have a break in the season now so hope to make a seperate exhaust for the 2 wastegates as i think the 3.5" exhaust is restricting the airflow out of the engine (exhaust boxes have expanded and blown out some rivets!). I have space constraints for this additional system though so expect this will take some time to get made.

I have 3 boost settings now, 1.9bar, 2.2bar and 2.6bar. On high boost, the power delivery is simply stunning! Instant response, almost negligable lag and a very quick car on corner exit!

I had to have the turbo seals replaced after Fintray Hillclmb so in the vids there's oil smoke which has now disappeared.

Here's some vids of the season so far:

http://www.youtube.com/watch?v=F3O4tyLnDlA

Wet run (hit the embankment which ruined the run):

http://www.youtube.com/watch?v=pZaTd8k2krY

This is the record breaking run at Prescott on high boost:

http://www.youtube.com/watch?v=-uZMMgn_B20

http://www.youtube.com/watch?v=GIqd1XZHNAA

http://www.youtube.com/watch?v=1zcHx3TGamY

Safe to say when she's not breaking shafts, she's very competitive now. Thanks to all who have contributed here, this wouldn't be half the car it is without the help! She's an animal now and i'm still learning how to drive her in anger!

As this is very much an on-going project, i will update as and when changes are made.

 

[zcchene46]

After reading this over again, I actually confused myself on all those boost numbers..
Mac initially ran 2.5bar total and 1.5bar from the turbo. Does it mean that the supercharger is working at a ratio that produces (2.5+1)/(1.5+1)=1.4bar? So (1.4-1)*14.7=5.88psi read on a boost gauge?
And then only (1.5-1)*14.7=7.35psi wastegate pressure on the turbo?

 

[zcchene46]

Actually I have more questions.
for a 1.6l/rev blower, it means that it is plumbing very closely 1.6 litter per revolution if the inlet air pressure is the atmospheric pressure; but what if it is being fed charged air of 2.5 bar (1.5 bar from the turbo plus 1 bar of the atmosphere)? Will it become 1.6*2.5=4l/rev?
And if we were to plot dots on a compressor map, which boost pressure should be used on the turbo map? the blower map? and what about the flow rate for either?

Thanks a lot!

 

[madmac666]

Being honest i haven't worked out any real maths of my system! I built it and made changes depending on the dyno results to get it working as it is!

Update: I have had 6 events in a row where the car and engine has not broken. Over these 6 events i have taken an FTD at Ingliston and set 4 new class records, often mixing with single-seater times lol. To say she's quick is an understatement now. Building the twincharger system is one of the best things i've done to the car in terms of the sport i compete in. The instant response, torque and driveability is just stunning and there is no lag at all on corner exit, or any time i have to lift off to keep traction.

Some more vids here:

http://www.youtube.com/user/evomadmac?feature=mhee

Almost at the end of the season for me and hopefully the car will stay reliable for the final round at Doune. Winter plans are to remove some excess weight from the car, but leave the engine and twincharger well alone!

 

[MikeHalloran]

The car makes beautiful noises. ... and makes me wish for longer hills.


Mike Halloran
Pembroke Pines, FL, USA

 

[Warpspeed]

A great achievement Donald.
With a lot of this stuff, raw engineering can only take you so far, the final bit is about tuning, tweaking, and optimization.

 

[madmac666]

She is sounding great just now, very crisp and free revving. I wish our hillclimbs were longer to give me a chance to really open her up. She's still road legal but it's too dangerous for public roads lol.

Warpspeed, when i put the twincharger together it was experience with my previous SC project and simply working out what i thought would be the best combo of SC and turbo. No real maths were done at all and surprisingly it worked quite well as it was. Developments such as belt drive and pulley ratios along with the larger turbo housing saw the system come to life in a way i never thought possible and i guess i was lucky the components were well matched at the outset!

Thanks for all your help again. This has been a learning experience like no other for me and i hope that sharing my project on here has helped others with their twincharger builds.

 

[patprimmer]

Mac

It's certainly helped me.

I think you short sell yourself by putting it down to a lot of luck.

There have obviously been some sound judgements on this.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[Warpspeed]

It's a funny thing Pat, but talented, determined, and hard working people tend to be more lucky than most.

 

[patprimmer]

There is always some element of luck, but certainly talent combined with hard work and determination certainly changes the ratio of good to bad luck dramatically.

Or to quote myself in another forum, when building an engine, if you leave anything to luck, you almost always have bad luck.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[madmac666]

Not sure about talented, certainly hard working and lucky hehe. I had my share of failures and learned by them. The worst was when the SC overheated due to the early bypass not opening at cruise throttle but i quickly worked out the reason and designed a safeguard to stop it happening again.

Thanks for the comments guys, i just wish i could take you for a run and let you experience what it feels like to go from 0-100mph in just over 5 seconds! It's very addictive lol

 

[madmac666]

.

 

[madmac666]

Not been here for a while due to work commitments so here's a quick update:

The season finished at the end of September at Loton Park with some great overall results. The engine and twincharger system has stayed in great shape for 8 events in a row. The only issue i had was a tensioner for the power steering belt broke away and left me with no power steering at Doune. The result was an mostly undrivable and dangerous car so i just teased her up the hill to get an official time for the event. Going into Doune, i was ahead in the ModProd Division by 2 points and my challenger didn't enter, so all i had to do was record a time for the Division win.

Final results:
Scottish Hillclimb Championship (SHC)
SHC class B3 winner
SHC Modprod Division Winner
SHC 5th overall - a place usually reserved for a single seater!
SHC Class records in B3 at Fintray, Doune and Forrestburn

Not a bad end to the season considering the reliability issues for the first half of the year.

I've been playing with pre-preg carbon parts. I made a complete dashboard that weighs only 1.7Kg as my oven and vac system is now operational and hope to make the complete underfloor in e-glass as the current fibreglass one weighs 40kg. I reckon i can get it down to 10kg including the bumpers.

In all, around 100Kg of weight is easily removable for the car which will make a huge difference to its performance. 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.