SR20DET

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SR20DET

Postby 7ish on Mon May 30, 2011 11:46 am

Hi guys,
I'm planning on starting a Locost build later this year and have been pondering engine choice for a long time now.

I'm planning on using a Nissan SR20DET engine, although admittedly I'm not *crazy* about the idea of a turbo in a 7. I do want a 4 sec (ish) car (0-100), so the 4AGE doesn't seem like enough. 160+kw Caterhams do 4sec 0-100...

Are there other affordable choices of N/A engines that can achieve 160+kw without a fortune spent on tuning? Obviously a smaller & lighter is preferable, so I'd want want to stay around the 2L size.

What kind of power can the Locost chassis handle be default?

Thanks in advance for any thoughts/advice etc
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Re: SR20DET

Postby 7ish on Tue May 31, 2011 7:35 am

hmmm, so after reading Wynand's thread about the 3SGTE, it seems to be a better fit than the Nissan.
Anyone know the weight difference between the two? From what I've read the 3S has a cast iron block and the SR20 has a aluminium block - that must effect the weight quite a bit...
Been Googling this morning but keep ending up on "tuners" forums where they talk like dey iz all from da hood! ugh. anyway...

Anyone have experience with these two engines? From what I've read they are both pretty strong, and good for way more power than I plan to have, so I guess the deciding factors would be 'ease of fitting' and 'weight'
Last edited by 7ish on Tue May 31, 2011 4:47 pm, edited 1 time in total.
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Re: SR20DET

Postby andredp on Tue May 31, 2011 5:16 pm

Also consider a Rotary, some of the non turbo models make really decent power.
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Re: SR20DET

Postby Joose on Wed Jun 01, 2011 9:24 am

From what I have read, most of the bigger engines (SR20, Toyota 3sgte?, Honda, Mazda engines, etc) are quite tall so you will struggle to fit them under the bonnet of a seven. You should budget from the start for a dry-sump arrangement if you plan on using any of these engines. Have you considered the Duratec and Zetec engines that the Caterhams use?
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Re: SR20DET

Postby muller on Wed Jun 01, 2011 10:40 am

Anton Guse is running the Nissan engine so worthwile having a chat to him, pm me for his number if you want.

As pointed out dry sumping will be required to make the engine fit and that adds significant costs
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Re: SR20DET

Postby Wynand on Wed Jun 01, 2011 8:42 pm

7ish wrote:hmmm, so after reading Wynand's thread about the 3SGTE, it seems to be a better fit than the Nissan....
Anyone know the weight difference between the two?


7ish, the 3SGTE fits into my chassis frame - flush level with bottom beam and about 30-40mm to spare below the bonnet without any modification of the sump. That said, my ride is based on the McSorley 442E chassis and I fabricated the top body parts - nosecone, scuttle and bonnet to fit the engine.....
However, with a Locost chassis and std GRP moldings you will have problems fitting this engine I assume and its best to take the posters advice to heart.

As for the weigh of the 3GSTE; the engine stripped of all manifolds, flywheel (as in my pics elsewhere) come to exactly 105kg which is a little better than the Zetec in same trim. But this engine can easily be upgraded to very serious HP without touching the bottom end, injectors etc.

FWIW, although my engine is rated at 165kw std (series 2) I will have it tuned down to about 145-150kw. Its better to have less power you can use to the full and enjoy rather than plenty you cannot put use and have a car that's un-drivable except for a straight line
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Re: SR20DET

Postby andredp on Thu Jun 02, 2011 6:06 am

Wynand wrote:FWIW, although my engine is rated at 165kw std (series 2) I will have it tuned down to about 145-150kw. Its better to have less power you can use to the full and enjoy rather than plenty you cannot put use and have a car that's un-drivable except for a straight line


Having it "tuned down" will basically require you to turn down the boost. It will not give you more driveability, only less power unfortunately. That is part of the problem with going forced induction. If you want more driveability, you will be better off fitting a smaller turbo, or some hybrid. This will make the turbo spin up faster, but ultimately run out of boost earlier in the rpm band producing less power.
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Re: SR20DET

Postby Wynand on Thu Jun 02, 2011 11:55 am

Thanks for the reply Andre.
In fact, I did plan to use a smaller turbo based on the T3/T4 flange - already have a wastegate and blow off valve for it, but going to stick with the factory turbo but with the BOV fitted to prevent turbo surge/lag when closing throttle.
At another forum where I have my build diary I posted my changes planned for the motor re turbo and the "resident" turbo expert - turbo tuner - reply with this and I quote verbatim.

As for the sizing, many people often make the mistake of sizing a turbo too small to help boost response. What happens is that you get a power/boost graph that looks like this: .......
This particular car has a very nasty tendency to spin the wheels when it comes on boost. This is because the boost ramps up so fast and gives a very non linear power delivery, then in the top end you run out of flow so what felt like a very lively motor all of a sudden fall over and feels very flat. This is not ideal and in reality you are much better to size the turbo to the motor.

To be honest, all this talk about having a responsive engine is kind of irrelevant, in a car that weighs as little as a 7 even a turbo motor without a turbo will have more than enough motivation to make it fun, and as such you won't even notice if it has a bit of lag, and on a race track if you have done your research on gear ratios you shouldn't have a a problem keeping it on boost.



What are your views on this reply/quote. Personally I do not think that a little less boost will hurt. I would rather have a car that has a linear supply of power when boost picks up than one that kicks when the boost arrive - imagine been in a traffic circle/turn when the boost suddenly arrive in abundance and the wheels spin :|
Normally the 3GSTE runs with 9psi boost but many turns it up between 12 - 17psi for blistering pace and some psycho's even go up to 20psi without touching the engine :shock: I plan to run 7-8psi and should I feel comfortable with more power, can always turn the boost up a bit 8)
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Re: SR20DET

Postby 7ish on Thu Jun 02, 2011 12:14 pm

Thanks for all the replies guys, much appreciated.
I had thought of fitting a smaller, faster-spooling turbo, or even a variable geometry turbo, but that obviously pushes costs right up. Not to mention the dry sump aspect (had thought of this, but hadn't yet looked into cost).

I stumbled across the "Aerocharger" recently which is a "zero lag" turbo, but moved on very quickly when I got to the price...

I have nothing against the AGE (who can argue with 8500 redline!), but I just don't like the idea of being limited in terms of tuning possibilities when I inevitably want to go a bit faster :twisted:

Obviously the aim is to have tractable power. Honda S2000 engine springs to mind, but where would you even find one of those? never mind what it would cost

Regarding Zetec or Duratec: could either of these be tuned to 150(ish) kw without costing the earth?

Thanks again...

[Edit]
As usual, google is your friend :) seems the duratec is pretty tunable, so maybe that's nto a bad starting point...
Last edited by 7ish on Thu Jun 02, 2011 12:31 pm, edited 1 time in total.
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Re: SR20DET

Postby andredp on Thu Jun 02, 2011 12:19 pm

What "turbo tuner" says makes sense, but remember it is all about what the driver of the car defines the response as. Fitting a smaller turbo will definitely get you into the boost quicker, and yes may also make the "kick in" feel stronger, but ultimately it will be less powerful.

My suggestion would be to use the engine as standard as possible including boost setting. The factory spend lots of money to get the engine as driveable as possible. If you then also use a proper engine management system (PP :wink: ) that can handle boost control, you can even let the boost come in slower if you feel the initial kick is too much.

No matter what you do though, if you are halfway through a turn and you give it boot and the turbo kicks in, you will be seriously sideways at the least :D Part of the fun and it is what quickly teach you some respect when you first take your baby you spend lots of money and time
Andre'
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Re: SR20DET

Postby andredp on Thu Jun 02, 2011 12:23 pm

7ish wrote:Obviously the aim is to have tractable power. Honda S2000 engine springs to mind, but where would you even find one of those? never mind what it would cost

Regarding Zetec or Duratec: could either of these be tuned to 150(ish) kw without costing the earth?

Thanks again...


S2000 you can find at the importers, around R30K when I saw one on the floor, still also a very tall engine and will most likely need dry sumping to fit in a standard Locost sized body.

Zetec and Duratec requires much $$$ to get to 150Kw, probably around R40K on imported bits.

Only way you are going to get to 150+Kw without spending huge bucks is either a turbo engine or a Rotary.
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Re: SR20DET

Postby 7ish on Thu Jun 02, 2011 2:03 pm

Thanks Andre.
Budget is key, so a big-money engine is not an option. Not now anyway...

Wynand - is your car drivable yet? If so, what is the 'drivability' like with that engine?

Anyone seen Toyota 2ZZ-GEs for sale anywhere?
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Re: SR20DET

Postby andredp on Thu Jun 02, 2011 2:49 pm

I have seen a 2ZZ-GE for R14K at the importers, but the engine looked real crap. Aparently they also only make about 90Kw on the wheels, a 20V with cams makes 90Kw on the wheels.

Maybe we would be able to assist better if we know what your budget is? Less then R10K for engine budget will not get you more then 80Kw(naturally aspirated) on the wheels on the highveld.
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Re: SR20DET

Postby 7ish on Fri Jun 03, 2011 9:57 am

I was thinking about 10k for the engine, but I could push it to 15k.
I had a look yesterday and saw a neat-looking 2ZZGE for 15k in the Junk Mail. Accordring to wikipedia, the 2ZZGE puts out 141kw (to the black top's 121kw). Surely transmission losses can't account for 50kw? I found a dyno chart for a 2ZZGE (in an MR2) which managed 137kw at the flywheel and 125kw at the wheels.

I think this might be the way to go...

So assuming what I've read is correct, and I could get a 141kw 2ZZGE for R15 000, can anyone speculate how that would compare to a R5000 4AGE with R10 000 work done on it? Obviously using the more common engine has it's advantages
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Re: SR20DET

Postby andredp on Fri Jun 03, 2011 10:10 am

Firstly Japan horses is a little bit smaller than those of the rest of the world ;) jk

No seriously, you can subtract about 30 - 35% from manufacturers flywheel figures to get what you may see here on the highveld on the wheels on a decent dyno. If you can source a decent 2ZZ for R15K it would be a good choice if the engine physically fits inside the body. Just remember that you will have to get a box that fits etc, all costs that can (hugely) add up.
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