Turbocharged cerebra ajp 4.5

[c3rba]

Latest images of this project

[c3rba]

[c3rba]

[c3rba]

[c3rba]

[Revvit]

Looks stunning!

I had a similar thought when re-building my engine with a view to replacing the problematic throttle bodies with something more contemporary.

Looking forward to seeing more photos as it progresses.

[Welshbeef]

Ha I love crazy fun ideas like this & then actually do it.

OP are the turbos twinscroll & hot V setup to reduce lag?
Also at what torque and power level from the motor does it become a little undrivable?

[ukkid35]

Amazing fabrication skills!

What is the purpose of the pump spacer?

[Byker28i]

Love the third photo, looks amazing.

[spitfire4v8]

Revvit said:

Looks stunning!

I had a similar thought when re-building my engine with a view to replacing the problematic throttle bodies with something more contemporary.

Looking forward to seeing more photos as it progresses.

The original AJP8 was on twin upstream throttles into plenums*, and they decided to go the uber expensive ITB route. There's a reason for that.

Having driven a Cerb on a plenum I can tell you the drivability is horrific.

Hopefully ICE have got some very mild cams ground up for this project with a much wider LSA, it's going to be a bucking bronco otherwise.

• I'm struggling to find my picture of it right now, but a plenum topped engine was on display in the old TVR Reception area, maybe someone has that pic somewhere ? I *think* that a picture of that engine was also on the wall behind al melling at one of his talks .. maybe the middle wallop talk ?

Edited by spitfire4v8 on Friday 5th July 08:46

[Dominic TVRetto]

Wouldn't the positive pressure generated by the turbos (even at idle/light throttle) contain the contaminated charge in the intake runners, and prevent cross-contamination via the plenum - as seen in the boosted RV8's where shunting usually disappears..?

[Revvit]

[TwinKam]

ukkid35 said:

Amazing fabrication skills!

What is the purpose of the pump spacer?

I would imagine, along with a correspondingly longer rotor pair, increased oil delivery.

[Jhonno]

Dominic TVRetto said:

Wouldn't the positive pressure generated by the turbos (even at idle/light throttle) contain the contaminated charge in the intake runners, and prevent cross-contamination via the plenum - as seen in the boosted RV8's where shunting usually disappears..?

I think Joolz was just referring to the N/A application..

[spitfire4v8]

Dominic TVRetto said:

Wouldn't the positive pressure generated by the turbos (even at idle/light throttle) contain the contaminated charge in the intake runners, and prevent cross-contamination via the plenum - as seen in the boosted RV8's where shunting usually disappears..?

For that to happen you'd have to have enough air passing the throttles to overcome the pressure of the exhaust gases migrating back into the intake on the overlap. Gas flows from areas of higher pressure to areas of lower pressure. For your scenario to happen the plenum would have to be at higher pressure , or at least equal pressure, to that which is existing in the combustion chamber on that overlap period. I can't see a turbo doing that, a positive displacement supercharger would though.

Now, there's several phases to that overlap period but condensed down it's essentially ..
initially the exhaust valve is open as the piston comes up, then before tdc the intake opens (overlap) , then exhaust gas can easily pass into the plenum because the plenum pressure is much lower than that in the chamber at that point, but after that the piston goes over tdc, the exhaust valve closes after that, as the piston goes down it's drawing air from the plenum into the chamber.

I don't see how you can stop the exhaust getting into the plenum until the pressure in the chamber is less than the plenum .. and for that to happen sooner you'd need a significant amount of air going past the butterfly into the plenum to raise its pressure.

I think the better manners of the turbo cars is a red herring, seeing as the vast majority would have been remapped anyway as part of the upgrade ?

[ukkid35]

c3rba said:

I don't understand what I'm looking at here, presumably this is the intake port, but that bears no relation to a standard head

Also, is there some sort of deck between the block and the head?

[Dominic TVRetto]

With my limited experience in "old-skool" turbo tuning, a cam with less overlap would often be chosen - reducing the period of overlap, but possibly meaning the intake valve would open later in the cycle..? Unsure here...

On the assumption the turbo didn't have a high boost threshold, and had been sized to promote quick response/spooling, I would have thought the amount of contaminant that reached the plenum would depend on:

- point of intake valve opening within the cycle
- therefore the volume of exhaust gas left in the cylinder when it opens
- and pressure generated by upward piston travel at that point in the cycle (distance/speed reduce the closer to TDC)
- volume of intake runner between valve and plenum
- angle of butterfly and associated charge flow
- charge pressure from turbo

...so specs of cam, manifold and turbo would play a large part in determining the amount of contamination at what rpm/throttle opening?

- Softer cam means less exhaust gas at less pressure
- earlier-spooling turbo means more charge pressure earlier in rpm range
- intake runner volume is "buffer" amount before contaminated gas enters plenum

As you say, given butterfly closure at idle that's probably not possible to stop contamination at that point, but a carefully specced build should surely be able to mitigate most of the drivability problems encountered in NA equivalents by equalising pressure in the plenum at low enough RPMs and throttle openings..?

Dom

[Jhonno]

ukkid35 said:

c3rba said:

I don't understand what I'm looking at here, presumably this is the intake port, but that bears no relation to a standard head

Also, is there some sort of deck between the block and the head?

It is the intake, they have flattened the floor of the port, as has been done before with success.

[spitfire4v8]

Dominic TVRetto said:

With my limited experience in "old-skool" turbo tuning, a cam with less overlap would often be chosen - reducing the period of overlap, but possibly meaning the intake valve would open later in the cycle..? Unsure here...

On the assumption the turbo didn't have a high boost threshold, and had been sized to promote quick response/spooling, I would have thought the amount of contaminant that reached the plenum would depend on:

- point of intake valve opening within the cycle
- therefore the volume of exhaust gas left in the cylinder when it opens
- and pressure generated by upward piston travel at that point in the cycle (distance/speed reduce the closer to TDC)
- volume of intake runner between valve and plenum
- angle of butterfly and associated charge flow
- charge pressure from turbo

...so specs of cam, manifold and turbo would play a large part in determining the amount of contamination at what rpm/throttle opening?

- Softer cam means less exhaust gas at less pressure
- earlier-spooling turbo means more charge pressure earlier in rpm range
- intake runner volume is "buffer" amount before contaminated gas enters plenum

As you say, given butterfly closure at idle that's probably not possible to stop contamination at that point, but a carefully specced build should surely be able to mitigate most of the drivability problems encountered in NA equivalents by equalising pressure in the plenum at low enough RPMs and throttle openings..?

Dom

I've never deliberately added pressured air to the plenum with a thought to drivability but I suspect you'd be on a one-way road to sky high idle and driving engine speeds seeing as the whole point of the butterfly is to limit the air going in to the plenum in the first place ..

[ukkid35]

Dominic TVRetto said:

With my limited experience in "old-skool" turbo tuning, a cam with less overlap would often be chosen - reducing the period of overlap, but possibly meaning the intake valve would open later in the cycle..? Unsure here...

Must get very expensive to fine tune on a SOHC engine