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4000GT

4000GT

New Member
Well, I am a bees **** away from buying this turbo. I really want 3,000rpm of usable range on full boost. I think a possible range might be 3,500 - 6,500rpm on this turbo. Opinions? Right now the power curve tips over at 5,500rpm on the dyno... Im thinking the turbo keeps the VE up in the higher rpm range and should extend it to 6,500rpm even with stock cams.

(stock bottom end, worked head)
 
I don't like your chances Andrew.....head porting will help but Erols work suggest it's the Intak,e m,anifold that's doing the damage.

No matter how much boost i run thru my motor the hp curve looks virtually identical...hp goes up with more psi but peak still occurs at the same rpm.

Seems that mass flow increases (more boost = more dense) but the increasing boundary layer thickness along the length of the runner causes a flow choke preventing the peak rp,m shifting higher in the rev range.

I always had the stock cams targetted as the culprit but after seeing the changes Erol achieved with just an intake change it seems the intake is likely the major prob.

Not that the stock intake is poor...i still make an easy 400+rwkw remember but with everything else staying the same an intake change could unlock alot of rwkw.
 
Yeah after seeing the massive gains the ITB guys were making... its a shame there isnt an intake out there that shortens the runners and corrects some of the geometry into the head while using the stock TB etc. Its quite surprising actually given the size of the market.
 
4000GT said:
Yeah after seeing the massive gains the ITB guys were making... its a shame there isnt an intake out there that shortens the runners and corrects some of the geometry into the head while using the stock TB etc. Its quite surprising actually given the size of the market.
Click to expand...

I am surprised no one has adapted the 2 stage VVti manifold to the earlier engines. The mating angle is different but should be solveable with some minor machining or a minimal adaptor plate.

The second stage shortens runner length substantially.
 
Im thinking it may be easier to keep the top half of the early plenum, take the top flange off the lower, and then route the runners directly down, instead of crossing. Probably means buying some tube for the runners, laser cutting a flange, buying some injector bosses and probably making new fuel rails... argh.
 
Andrew,
I would be interested in seeing the results of the A1-turbo ITB manifold castings with short bellmouths, 2 seperate plenums to 2 - 58/60mm TB's used on a turbo engine.

At around $1000 a pair they are not to expensive but do need a lot of work to get the dia's up and port matching. Then there are the plenums to be made.

I am confident you would see a 20% increase in power plus 7500/8000 rpm.
Any takers? How about it Justen - 480rwkw ? :wavey:
 
Well yeah I guess you could use the bottom casting then you can use the stock fuel lines, then make a plenum on top of those. I would be inclined to use the existing TB in its current place for pipe routing and ease factors.

I have 2 spare sets of heads here now just begging to be used!

Are you suggesting 20% over the range without any other mods?
 
It's tempting....I would just go a single large plenum though with the stock throttle body same as Andrew suggested, what about that?

I'm sure i could get some CNC'd flange plates cheaper than $1K/pair though?
 
How about boxing the lower intake ??
and bellmouthing the lower manifold ports ...
Then fitting throttle body where ever you wanted...
This done on amny pushrod G.M and Fords..
Esp where the lower is truck style...
Long and big ports.. Boxing them makes them short and big...
 
Doesn't help XR? the top section is just a plenum anyways so this option does nothing to chan ge the runner issue. You either need to enlarge the runners eg extrude hone; or shorten them.
 
My mate doing the heads had a look at them today, doesnt seem too worried about the intake angles actually, and seems to think the stock head design will respond well to some porting. Will be interesting to see.
 
im hoping for 3500 to 6500 with the upcoming gt42r with 1.01ex. any sooner would be a bonus.
justen what is your rev limit atm?
 
peak hp is around 5400rpm so not much point revving too much past there....will rev to 7000 but to what end.

With some intake work though will rev out to 7000 and some big gains to be had
 
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