Individual Throttle Bodies vs. "Flowed" Carrera Intake Manifold

[Roamer]

Ok guys, further questions regarding my proposed build up . . .

I am trying to plan my attack for a 300hp na motor based upon my stock 86 3.2. My plan is to enlarger her to 3.4 liters, use ~10.5:1 compression pistons, twin plug, aftermarket engine management (DTA, SDS or Electromotive), a hotter cam (GE-60, S or an Elgin Super C-2 Grind) and port and polished heads all with my current SSIs.

One of the most expensive components that I have investigated are the individual throttle bodies. Most go for $2500-3000.

What I want to know is what kind of difference in power should I expect vs. a "flowed" Carrera intake manifold with a MAP sensor (Aftermarket engine managment). Ultimately I need to know if this is the big factor in taking a high comp 3.4 from ~260-270hp to 300.

Any advice would be appreciated!!

[CamB]

I reckon you need more than S cams - possibly GE80?? I've got about 270hp from the equivalent 3.2 (Sc crank, 98mm p&c) with S cams. I might have picked about 5-10 hp with a sport muffler.

I can't answer your question about the throttle bodies though!!!

[Steve@Rennsport]

Roamer:

As a data point for you, we recently did a 3.4 here with 10.9:1, 120/104 Webcams, Carrera heads that we did here, twin-ignition, headers w/flowmaster race muffler, and our own 48mm tall butterfly FI intake with DTA management. This made 330 HP on our Superflow engine dyno.

I'll let you draw your own conclusions,.....

[emcon5]

Damn Steve, you and your toys.


At what RPM?

My concern for something like that is all the power would be up high, and noty very "streetable".

Tom

[Steve@Rennsport]

Hi Tom:

LOL,........This engine has a pretty flat torque curve from 3500 to 7000 with peak torque 265 lb-ft at 6100. Peak power was at 7400.

For a race motor, its VERY well behaved with no ill manners.

Ahhhh,... the beauty of good induction, precise mapping, and proper engine management.

[Roamer]

Thanks Steve, I was hoping you would pipe in!

Given my desire to make this more of a street motor, I am willing to take a 20-30hp hit with less aggressive cams. Clearly the TB's and good cams are the step that takes it to another level.

Maybe I will drop you a line to inquire as to DTA and TB pricing.

Thanks to all!

[CamB]

Ooops, I wasn't very clear. I meant I might be able to pick up another 5-10hp with a sport muffler (ie more like 280hp). I guess then the extra 6% displacement would make it almost 300hp.

Mine is streetable - no problem (low weight, big engine).

And of course, I just paid someone to do mine --> I'm no expert, but Steve is . Listen to him.

[Roamer]

Cam, I am very interested in your build up. Could you provide more details? If I understand you correctly, do you have a SC motor with 98mm high comp P&C's and twin plugs? If so, what modifications were made to the stock intake? Do you have aftermarket engine management?

The reason I ask is because I am also considering just swapping out high comp 95mm pistons. $2000 is a lot of dough for a 6% power increase. The money may be better spent on the intake.

There seem to be a lot of ways to skin the cat, I am just looking for the most cost effective and "liveable" solution.

[dwightp]

Roamer:

I've done both. Right now I'm trying to get a TB setup to work. Albiet, I think I'm the victim of improper sizing and parts. I've got a modified 3.2l intake that I'm seriously considering going back too. If someone were to buy my TB's now, my decision is made. I'd recommend that you get an opinion from someone that has a fully installed set-up and can give you a driveability assessment!!! Engine dyno results are just that, engine dyno results. Not an installed result. I witnessed a HP increase but it wasn't huge. It did (TB's) give the power curve more meat at higher RPM on the dyno. Given the trade off's would I do it again?
Maybe, BUT I'D BE SURE that those that are providing the TB solution are complete and thorough. Briefing you on what you loose, offering complete solutions to heat (if desired), linkage, fuel system mods and filters. Nothing's more frustrating in spending $3k + for TB's, + dyno time and find out that you are left with those problems to resolve! Make sure it can IDLE too! At least if you have any street driving planned.

For the TB's, consider support for heat and brake boost, linkage, fuel system mods, loss of cruise, loss of A/C, plans for oil and fuel vent mods. No one has been able to offer (at least yet) a viable off the shelf solution for my brakes and linkage problems with the TB's. I went to various suppliers for fuel line fitting adapters.

The TB's sound awesome and will give some HP increase IF DESIGNED RIGHT, but it's at a price.

You undoubtedly note some of my frustration. Hopefuly in a few month's I'll be more optimistic and can convey that to you. Just one lister to another. My .02 worth.

Best of luck!

[CamB]

If so, what modifications were made to the stock intake? Do you have aftermarket engine management?

The intake is MFI bored (to 40mm) and modified to take EFI injectors. This solved dwight's linkage problem (effectively using stock parts). I have unassisted brakes and early heat exchangers (it is in the '69). Converting the car from carb fuel lines etc to EFI caused the mechanic some grief, but not much.

Cruise and A/C were there to start with either!

I needed new P&Cs (the engine was sold by the mechanic second hand and had SC cylinders with 95mm JE pistons which were very very noisy when cold, which didn't suit me as it is a street car), so there was no price penalty for me to get 98mm vs 95mm Mahles.

It looks like this:

[Wayne 962]

With a really hot cam, you will have potential problems with fuel reversion affecting your other cylinders. The individual throttle boddies separate the intake charges from the rest of the cylinders, and allow you to run a really hot cam with limited side effects on the other cylinders. In general, I would think that you would have some problems using a shared manifold setup like the stock 3.2, with anything like an 'S' cam or hotter. I don't typically recommend using these cams with that manifold.

Steve, want to weigh in on this?

-Wayne

[Steve@Rennsport]

I agree.

If one wishes to use a cam hotter than the T, or 964, then one must use a 6-butterfly intake system of some kind; carbs, MFI, TWM or our six-throttle setup, and of course the 993 RSR.

If you use a hot cam with any single throttle large plenun intake, you'll have very poor throttle response below 4500 and poor HP until 5000+. BTDT,....

[Roamer]

Originally posted by dwightp
Roamer:

For the TB's, consider support for heat and brake boost, linkage, fuel system mods, loss of cruise, loss of A/C, plans for oil and fuel vent mods. No one has been able to offer (at least yet) a viable off the shelf solution for my brakes and linkage problems with the TB's. I went to various suppliers for fuel line fitting adapters.

Steve or Wayne, can these issued be resolved for street use of TB's? I need heat, brake boost and the oil/fuel venting. A/C is being removed and cruise has not worked since I owned the car, so no skin off my back. I think the linkage issue is not that bad with some of the Porsche TB kits (Jenvey or TWM). However, this car needs to be friendly on the street and "daily drivable". I am willing to go with less agressive cams to give me better idle and take the hp hit, but I still need to be able to take my wife and daughter out for ice cream.

As with Dwight, I don't want to find myself spending $3k only to find that I don't like the "car".

[beepbeep]

I'll give my pedestrian view on this (No expirience whatsoever):

As far as i know, TB's don't give any drastic HP increase but slightly better throttle responce. I believe BMW stated that they didn't win any HP on their M3's with TB's ... just better pickup. Also, running TB's means that there is no good source of vacuum, so:

1. It's hard to plumb in brake booster
2. EFI you are planning to use will probably need to use Alpha-N, beacuse connecting MAP-sensor to those short stacks underneath TB will provide very noisy signal at low revs = BAD idle.

Now this is completly my opinion and i'm not an expert in any way, which many of genltemans posting in this thread are...but i would actually skip TB's...it's just too much money to do justice.

I would use good port-matched Carrera plenum...i beieve performance would be the same and all that extra volume would smoothen the vacuum, allowing you to use MAP-based ECU which is arguably easier to map...or Alpha-N/MAP blended mode. And yes, there are no TB syncronisation issues to worry about.

TB's are cool though.

[Roamer]

Thanks Goran.

However, I am trying to figure out where all the hp is coming from when Steve is getting 330 hp from a high comp 3.4 with a slightly aggressive cam and TB's while the accepted norm for a high comp 3.4 with twin plugs and standard cam is ~260hp. 70 hp is not coming out of thin air and most people state that a Carrera intake, even with improvements will not get you anywhere near that hp jump.

If I can get a more agressive cam like the Elgin Super C-2 or the Webcam 20/21, up the compression to 10.5, twin plug and convert to mass air with aftermarket engine management and get close to 300hp out of a 3.4, that would be fine, but I don't think that is realistic. From what I can tell the Carrera intake and less agressive cams that must be used with that intake really hurt the hp.

If you look at the history of RSR motors, the real screamers are those with "S" cams, twin plugs, individual throttles and ~10.3:1 compression. While BMW claims that the throttle bodies did not increase hp that much, you have to consider that they have been using variable intakes and cams that can compensate for the pulses the agressive cam timing at high rpms.

I just want to know what puts me over that 260-270hp hump and what price do I pay. If I am only going to get 260hp I would rather just put in a more aggressive cam and mass air sensor on the motor as is and get ~240-245hp and save $5000. For $5000 I need to get near 300hp to make it worthwhile in my mind.

[MoreGAS]

Roamer,
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However, I am trying to figure out where all the hp is coming from when Steve is getting 330 hp from a high comp 3.4 with a slightly aggressive cam and TB's while the accepted norm for a high comp 3.4 with twin plugs and standard cam is ~260hp. 70 hp is not coming out of thin air and most people state that a Carrera intake, even with improvements will not get you anywhere near that hp jump.
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Look at his post- fairly BIG cams with quite bit of overlap netting peak hp at 7400. Also Good headwork, headers of unstated size and quality but surely not whimpy SSI's the street guys are fond of, with a racing muffler the barely squeeks under Portlands public park 98 or 100 DB limit. 11:1 no little bump in compression. Then proper fueling (no small thing)and multiple butterfly throttle bodies to get the loads of air the engine is asking for with cam and RPM. It is "only" several small things, quite a bit better, to get this huge difference(when you think of it as a percentage).

As far a race engines(or any) potential, think of the specific output in Hp /Litre. 330 Hp from a 3.4 is about 90-95 Hp per L, not bad Steve. Porsche from their RSR 3.0 with slide valve got 110 Hp/L. There are some diminishing marginal returns here with the thermal capacity of the engine being exceeded with our poor overtasked air cooled 911 engines as they get bigger and bigger. The factory RSR's at 3.8 L made about 375 in a form Porsche Motorsport believed the thing would last 24 hrs . Stock form they were around 340 hp. The broadness of the HP curves and the Tqe have been totally neglected here and THIs is really important as we don't live among the peaks-especially on the street.

Kevin Roush
GAS Motorsport
Performance Porsche
909 985 2909

[MoreGAS]

If you look at the history of RSR motors, the real screamers are those with "S" cams, twin plugs, individual throttles and ~10.3:1 compression. While BMW claims that the throttle bodies did not increase hp that much, you have to consider that they have been using variable intakes and cams that can compensate for the pulses the agressive cam timing at high rpms.

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Oh yah- The RSR's used RSR or more camhafts- not the "S" streeter cam.

Kevin
GAS Motorsport

[Roamer]

Kevin, I agree that the 330 is the culmination of good work by Steve, what I would like to know is how much could be adaptable to a street motor and what power levels are we talking about? Also, IYO, are throttle bodies adapatable to the street?

[CamB]

Oh yah- The RSR's used RSR or more camhafts- not the "S" streeter cam.

Kevin
GAS Motorsport

And made max power at something like 7500 or 8000rpm. My S cammed engine makes max power at 6300rpm, from memory.

[Tim Walsh]

Actually according to BA max HP for the RS (s cammed) is at 6500rpm and RSR is at 8000 rpms. That's not redline but max HP. If the S cam has another 800 rpms past it's redline then the factory RSR had a redline of what, 9000RPMS?