Toyspeed.org.nz Message Board

by **Rookie** » Mon Jul 05, 2010 11:28 am

Hey,
I'm looking at building a 4AGTE out of a blacktop, and I was wondering what sort of compression ratio I could expect if I used silver top pistons? I know you will probably all just say go 4AGZE pistons, but I'm not going to be chasing huge power (the car is a lotus 7 so any more than 250 hp is pointless). I'm going to use silvertop rods, and I picked up a set with pistons for $70.

Cheers
Dave

by **blindnz** » Mon Jul 05, 2010 11:59 am

if you haven't yet spent the money on the blacktop. buy this.

http://www.trademe.co.nz/Trade-Me-Motors/Car-parts-accessories/Toyota/Engines/auction-301367480.htm

Hows the 7 going? thrown out the crossflow?

by **Rookie** » Mon Jul 05, 2010 12:37 pm

Hey, I've already got a blacktop, but yea the kent will stay where it is untill I get this engine completely sorted.

Dave

by **rollaholic** » Mon Jul 05, 2010 5:32 pm

people say 4AGZE pistons for a reason, they give you a compression drop (the difference between blacktop and silvertop is minimal) they are CHEAP and they are sturdy, particularly in what sounds like it will be a reasonably mild setup. get the high comp GZE piston and never worry about it again!

by **Rookie** » Mon Jul 05, 2010 5:56 pm

I was asking what the compression ratio would be because, there should be a sizeable difference, seeing as the heads have very different combustion chambers, and the pistons have different compression heights, I would expect the silvertop pistons to drop the compression ratio to 10:1 or even lower, but I am asking if anyone KNOWS what the drop will be.

Dave

by **Crampy** » Mon Jul 05, 2010 7:57 pm

I've seen a stock Silvertop supercharged with a Rotex supercharger. Made pretty good power.

Also a guy on here turboed his Silvertop AE101 and got ~145ish kw at the wheels at low boost (like 4-5 psi) with a TDO5H from memory, tuned with a Link ECU. That was quite a few years ago though.

by **Crampy** » Mon Jul 05, 2010 8:01 pm

here:
http://www.youtube.com/watch?v=sPIaXDlExaE

Now from what I read on the build thread on this car, the engine was a stock silvertop to start with, but they have since rebuilt it with 4AGZE pistons and retuned it.

EDIT: As in the video. 14psi boost with 10.5:1 compression.

by **shihad** » Tue Jul 06, 2010 3:06 pm

Crampy those rotexs look insane I want one anyone know the price on one of those kits? couldnt find one in my quick looking on their website.

by **Rookie** » Tue Jul 06, 2010 3:11 pm

Thanks to some help off another site, I'm pretty sure that the compression ratio with silvertop pistons in a blacktop will be 9.94:1, which should make a perfect combo for good off boost response and good boosted reliability.

Dave

OMG so shiny! · by **Dell'Orto** » Tue Jul 06, 2010 6:24 pm

Yeah if you're not chasing big power that CR will be fine. Will be interesting to see how stock silvertop pistons hold up to boost.

by **KinLoud** » Tue Jul 06, 2010 8:34 pm

I get 9.99 compression, pretty close to your 9.94! - what website did you look at?
They must have done their home work like I have!

Ken

by **matt dunn** » Tue Jul 06, 2010 8:44 pm

what is the std compression of a BT and a ST?

by **metal_sean_head** » Tue Jul 06, 2010 8:47 pm

matt dunn wrote:what is the std compression of a BT and a ST?

ST: 10.5:1

BT: 11:1

Well thats what i found on the net. Don't take it as gospel.

by **rollaholic** » Wed Jul 07, 2010 8:52 am

some may remember zaks AE85 with the supercharged silvertop - alleged 150kw on standard engine, and that saw plenty of abuse in tinys hands

nothing wrong with a bit of compression, just need to be careful... i havent seen him post for a while but bazda knows a fair bit about various 4age / 7age combos. matt dunn is another good one to talk to. i'd have thought for a race car you would want bullet proof, not possible hand grenade. but thats just me

by **matt dunn** » Wed Jul 07, 2010 8:05 pm

rollaholic wrote: matt dunn is another good one to talk to. i'd have thought for a race car you would want bullet proof, not possible hand grenade. but thats just me

I do have a program that i made to work it all out,
when I get a bit of time I will have a go and work it out.

I would run my race car at 10:1 comp ratio with 20psi if i could get it there.

Have seen a std silvertop take a fair amount of boost with good sucess,
it's all in the tune.

Matt

by **Rookie** » Wed Jul 07, 2010 9:50 pm

Hey guys cheers for the responses, I got the info for the head cc's off toymods. Yea 10:1 should be good but if detonation does become a problem, i will just fit a thicker head gasket, it will be interesting to see what it goes like. who said anything about a race car? its a road car (albeit a fast one). Matt what do you mean "its all in the tune"? I've heard it said by a few people that know what they are doing before, is there something special that "unlocks" horsepower aside from getting the AFR and timing right?

Dave

by **Crampy** » Wed Jul 07, 2010 9:54 pm

Rookie wrote:Hey guys cheers for the responses, I got the info for the head cc's off toymods. Yea 10:1 should be good but if detonation does become a problem, i will just fit a thicker head gasket, it will be interesting to see what it goes like. who said anything about a race car? its a road car (albeit a fast one). Matt what do you mean "its all in the tune"? I've heard it said by a few people that know what they are doing before, is there something special that "unlocks" horsepower aside from getting the AFR and timing right?

Dave

The tune will be the difference between a nice running engine and one that is a bag of $hit (or a bag of bolts and metal filings).

People expect too much out of motors and then wonder why they drop the guts over the tarmac. As long as you are realistic, it will work well for you.

by **matt dunn** » Wed Jul 07, 2010 10:19 pm

Rookie wrote: should be good but if detonation does become a problem, i will just fit a thicker head gasket
Dave

Fitting a thicker gasket is not the answer!!

The answer is to tune it so that it does not detonate!!

When people say it is all in the tune, they are not always talking HP,
they mean HP and Reliability.

If it detonates, the drop some ignition timing out of it, or richen the mixture, or some of the other tricks tuners do.
that why you tune it, so it will run without damaging itself.
It's not "unlocking the HP" it's " preventing destruction"

Hell we ran a 3SFE Turbo motor with reasonable boost on near 12:1 comp ratio as an endurance car years ago. Mr Revhead would remember that.

by **Crampy** » Wed Jul 07, 2010 10:23 pm

Exactly.
Compression + boost is seen as this bad thing and everyone says it wont work.
The thing is, it does. The tune is the most vital thing when it comes to a stressed motor.

by **MAGN1T** » Wed Jul 07, 2010 11:01 pm

Apart from your choice of fuel.

Steve

Toyspeed.org.nz Message Board

Blacktop 4AGTE pistons?

Blacktop 4AGTE pistons?

Who is online