10-13-2004, 06:15 PM
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Senior Member
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Join Date: Oct 2003
Location: Summerville, South Carolina
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Twin Spark Engine Swap Alternatives
Hi,
I've done a little research on the model 75 TS conversion for GTV's and such but I'm still searching for more info and ideas. This is why I'm starting this thread, so I can get others view points and experience. I've talked with Bruce Colby, Jim Steck, Marc Mosko, Kevin of E.B. Spares and various others. I've also read every thread on the BB about it. The options are many. There are systems made up by Jim Steck, E.B. Spares, AH Motorsports, and maybe others. I asked Kevin of EB Spares to give me a cost versus performance scenario and the list below is what he came up with. I told him I was aiming for a hot street setup, not an all out racer.
1. Fit TS with stock fuel inj./ign.
2. Fit TS with stock fuel inj./ign. and a set of 12mm 280 cams.
3. Fit TS with 40's, stock ign. (ecu won't know its not running fuel inj.)
4. Fit TS with 40's, stock ign. and a set of 12mm 280 cams
5. Fit TS with 40's, 12mm 280's and Jim Steck's Nissan distributor
6. Fit TS with 45's 11.4mm 300 degree and mappable ignition
7. Fit TS with full mappable ignition and fuel injection.
That sums up Kevin's response. There are also other things to consider such as forged pistons, performance valve springs, Carillo rods, lightening the flywheel, fitting a good clutch, etc.
I believe Jim Steck has created numerous TS systems of all flavors using a modified Spica intake manifold, or the AHM supplied manifold which will accept either carbs or fuel injection. The ignitioin systems vary as well. You can keep the existing dual distributor setup if room permits, or choose Jim's single modified Nissan distributor or choose a fully mapable direct fire setup. I've asked for details on the EB Spares and AHM direct fire FI setup but never get an indepth reply, but I may not be formulating my questions correctly since I'm not an engine guru like many others on this board.
My questions:
1. What is the simple performance difference between Weber 40's or 45's if properly setup?
2. Is one or the other better for street and why?
3. What kind of gain in performance will fuel injection have over the carbs? 4. Is it worth the money to go with FI over carbs?
5. What brands and models of FI are there available for the TS conversion?
6. Are there other intake manifolds that will work with either the carbs or FI?
7. For street use, what benefit would a direct fire mapable ignition system grant me?
8. What brands and models of direct fire ignition systems are there out there that'll work with the TS conversion?
My last car was a '73 GTV fitted with Borgo 10.4:1 pistons, Euro cams, Shankle header, and a stock and properly tuned Spica. It was very nice but I always wanted more ummph low and high. Folks sold me on the TS idea. I just want some additional advice on what folks think a great street setup would be.
I know this is a long post. Thanks for looking and I look forward to seeing the responses.
__________________
Dale Thomas
1969 1750 GTV (Giallo Ocra)
Summerville, South Carolina
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10-13-2004, 07:53 PM
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Location: Northampton, MA
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My .002 FWIW
My spider has a pretty much stock TS with Jim Steck's headers and nissan distributor with stock Motronic EFI. When I stomp on the gas and get pushed back into my seat, its a beautiful thing!
You may not be an engine guru, but I'm a full fledged idiot. For me the TS spider is an ongoing learning experience. This Winter's project is to get myself smart enough to install megasquirt, maybe with some larger injectors. In my mind, programmable fuel injection is the best of all worlds in terms of power and reliability.
My hope is that we'll get some smart folks contributing info here that will make this project smoother for us.
In the words of that great American Dave Chapelle: "Twinspark? Ummm, umm beyitch. Good ****in choice, Mother****a"
__________________
92 Spider Veloce
71 TwinSpark Spider - Soon to be 4 Sale
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10-14-2004, 07:00 AM
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I'm going through this decision process myself. My last conversation (yesterday) with Kevin at EB Spares has left me confused. My target is similar to yours... somewhere around 170 useable HP with good torque. Both Anthony and Kevin have suggested that I can get a streetable reliable single spark engine with that type of power with 45mm Carbs, GTA type headers, large valves, cams (11 or 12mm depending on source) and either stock or 10.4 pistons. Kevin was saying that to get that kind of reliable power from a twin spark requires forged pistons and H section con rods in addition to the 45mm carbs and 300 degree cam. Since it looks like it will cost over $1000 to get the twin spark engine before rebuild costs, and the cost of the mods to get to about 170 HP is higher, it seem like modifying the single spark is the best/cheapest alternative. This doesn't seem to make sense, since starting off the twin spark has more HP.
My turn for a looong post!
__________________
Ken Lee
Oakville, ON
1974 GTV 2000 - Ruby (I'm never selling this one, honest!)
1973 GTV 2000 - Rowdy (or this one I hope)
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10-14-2004, 05:16 PM
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Senior Member
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Join Date: Oct 2003
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 Quote:
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Originally Posted by Paradiso
You may not be an engine guru, but I'm a full fledged idiot.... In the words of that great American Dave Chapelle: "Twinspark? Ummm, umm beyitch. Good ****in choice, Mother****a"
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I think it was said best in Blazing Saddles; "...you use your tongue prettier than a twenty dollar *****."
Seriously though, thanks for responding. Did you have your regular engine dyno'd prior to swap and then have your new engine dyno'd? If not, what difference would you say there was? Now for a silly question...What kind of gas mileage are you getting? Have you considered going with performance cams?
You should post an engine bay pic for us and give us more details as to any lessons learned in the process and such.
Contact me anytime at dale.thomas@cox.net to discuss TS stuff or just Alfa stuff.
Best wishes.
__________________
Dale Thomas
1969 1750 GTV (Giallo Ocra)
Summerville, South Carolina
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10-14-2004, 05:32 PM
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Quote:
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Originally Posted by GTV4EVR
Kevin was saying that to get that kind of reliable power from a twin spark requires forged pistons and H section con rods in addition to the 45mm carbs and 300 degree cam. Since it looks like it will cost over $1000 to get the twin spark engine before rebuild costs, and the cost of the mods to get to about 170 HP is higher, it seem like modifying the single spark is the best/cheapest alternative. This doesn't seem to make sense, since starting off the twin spark has more HP.
My turn for a looong post!
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That doesn't sound right does it. If the engines were outfitted similarly, the TS should outperform the standard engine. I thought the H section rods just provided for a higher revving engine, which would of course allow for more power. I'd pose the question to Kevin again and ask him to clarify. There may be some misunderstanding. Bruce Colby and Jim Steck are good folks to ask as well. Let's see if some of the engine guru big heads join in and steer us right.
Let's keep in touch.
__________________
Dale Thomas
1969 1750 GTV (Giallo Ocra)
Summerville, South Carolina
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10-14-2004, 07:19 PM
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Location: Vista, CA
Posts: 770
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Quote:
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Originally Posted by Dale
My questions:
1. What is the simple performance difference between Weber 40's or 45's if properly setup?
2. Is one or the other better for street and why?
3. What kind of gain in performance will fuel injection have over the carbs? 4. Is it worth the money to go with FI over carbs?
5. What brands and models of FI are there available for the TS conversion?
6. Are there other intake manifolds that will work with either the carbs or FI?
7. For street use, what benefit would a direct fire mapable ignition system grant me?
8. What brands and models of direct fire ignition systems are there out there that'll work with the TS conversion?
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1. 45's will move your peak power to a higher rpm. How much higher will depend on the choke size. They come with 36's I think. That's good for a peak power in a 2-L at about 6500 rpm. This is a bit up from a stock TS power band so to make use of 45's, you'll need more a bit cam, and a bit more compression wouldn't hurt.
2. What you give up with 45's is some low and mid range performance. Low and mid range is where you'll drive on the street so you'll miss it there. You will be able to drive on the street, it just won't be quite as nice.
3. When you say FI here I'm assuming something other than the Motronic FI that came with the engine but I think my answer covers them all. FI properly set up will run cleaner, neater and harder than carbs. This is especially true at lower rpms associated with street driving if we're talking 40/45 DCOE’s. You can get pretty good top end performance out of either but full-on programmable FI is easier to change/tune because you don't need a bunch of jets, etc. The stock FI with the stock cams or the slightly hotter C&B street cams will run great without any messing around past making sure everything is working properly. If the setup you want needs more fuel and air than the Motronic unit can provide, then you need to go to carbs or programmable FI to get it. Programmable FI is more flexible and more expensive. (A quick note here: most of the commercial programmable FI systems are full engine management systems so you get ignition as well.)
4. There is no universally correct answer to this question. You will have to decide how much $ is right for you.
5. There are a bunch of FI/engine management systems on the market. Check the Milano/75 threads. They seem to have a good grasp of this. If you decide to go this way, start with a very solid checking account and plan on learning a great deal about FI fundamentals, components, electronics and potentially programming.
6. The only production one I am aware of is the AHM manifold sold by themselves and EB Spares. Past that you are on your own but it's not hard to do.
7. From a practical stand point, some but not a lot. You have fewer moving parts which is nice. But you have more complex system which could be a problem to sort out. Then there are a bunch of approaches that are in between. It would also cost more $ but, hey, it's your $!
8. Again, check with the Milano/75 threads.
I’m sure this will incite a lot of conversation. There is simply no "perfect" solution to all this. It's all a tradeoff, $ vs performance, street vs track. Just what gear heads love!
__________________
Bruce Colby
Competition Director, AROSC
'65 Sprint GT (TS race)
'69 1750 GTV (TS street)
'71 Jr. Z (special occasions)
'89 E30 (the dark side)
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'69 1750 Spider (sold  )
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10-14-2004, 08:04 PM
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Bruce,
You always give great indepth answers in plain language. I like that. I thought I'd move some of my questions to you here on the BB so others can gain from your experience and the experience of others. I know there are a fair number of folks out there taking on the TS swap challenge that can benefit. Maybe the best first solution is to try the stock Bosch setup, then if that isn't enough then try the C&B modified street cams. If that isn't enough, then maybe go on from there....forged pistons, etc. That is certainly the best route if one doesn't want to put their wallet into shock.
Have you checked out my post on MicroBlue?
Thanks for the info. We'll talk some more!
__________________
Dale Thomas
1969 1750 GTV (Giallo Ocra)
Summerville, South Carolina
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10-15-2004, 06:47 AM
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Senior Member
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Join Date: May 2003
Location: Oakville ON
Posts: 1,762
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Quote:
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Originally Posted by Dale
Ken,
That doesn't sound right does it. If the engines were outfitted similarly, the TS should outperform the standard engine. I thought the H section rods just provided for a higher revving engine, which would of course allow for more power. I'd pose the question to Kevin again and ask him to clarify. There may be some misunderstanding. Bruce Colby and Jim Steck are good folks to ask as well. Let's see if some of the engine guru big heads join in and steer us right.
Let's keep in touch.
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__________________
Ken Lee
Oakville, ON
1974 GTV 2000 - Ruby (I'm never selling this one, honest!)
1973 GTV 2000 - Rowdy (or this one I hope)
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10-15-2004, 06:55 AM
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Senior Member
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Join Date: May 2003
Location: Oakville ON
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Quote:
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Originally Posted by Dale
Bruce,
Maybe the best first solution is to try the stock Bosch setup, then if that isn't enough then try the C&B modified street cams. If that isn't enough, then maybe go on from there....forged pistons, etc. That is certainly the best route if one doesn't want to put their wallet into shock.
Have you checked out my post on MicroBlue?
Thanks for the info. We'll talk some more!
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Any suggestions about where to find more info to help round out my TS education? I have posted questions here in the Milano/75 sections, but never got any replies.
Thanks
__________________
Ken Lee
Oakville, ON
1974 GTV 2000 - Ruby (I'm never selling this one, honest!)
1973 GTV 2000 - Rowdy (or this one I hope)
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10-15-2004, 09:55 AM
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Registered User
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Join Date: Feb 2003
Location: Vista, CA
Posts: 770
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Quote:
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Originally Posted by Dale
Bruce,
... Maybe the best first solution is to try the stock Bosch setup, then if that isn't enough then try the C&B modified street cams. If that isn't enough, then maybe go on from there....forged pistons, etc. That is certainly the best route if one doesn't want to put their wallet into shock.
Have you checked out my post on MicroBlue?
Thanks for the info. We'll talk some more!
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The first problem was surging at idle. The engine would start fine and run fine but, when it dropped back to idle, it would nearly die, then speed up to about 2000 rpm, then repeat the process. Normally, one would expect an air leak but I sure couldn't find one. Another possibility was that the idle air valve (the valve the ECU uses to control idle rpm) wasn't functioning properly. It opened and closed when voltage was applied but I didn't know if it was behaving properly. I had/have no specs on this. I tried a couple other used valves and they both did the same thing so I gave up and went back to leak detecting. Finally, I happened onto another idle air valve and it was much quicker to respond to voltage input so I tired it. Problem solved; lesson learned.
I didn't even know I had the other two problems until I put the car on a dyno. The high rpm output turned out somewhat lower than expected but not a whole lot. It was a chassie dyno so it was looking at rear wheel bhp rather than power at the flywheel. All the specs I've seen are flywheel power and, because I really don't know what the drive train power losses are, I wasn't sure exactly what to expect at the wheels. At any rate, I thought the car drove great at this point. After some fussing I found two things. One was a duff set of used spark plug wires (I should have known better!); the other was the angle at which I had mounted the "Steck dumb distributor". It seems the distributor body was to rotated too far clockwise (retarded) and at high rpms there was sufficient spark advance (spark occurs when rotator is more counter clockwise) that the spark apparently had to make quit a jump inside the cap before it got to the plug. Fixing these two problems was very noticeable when driving but I don't have any dyno data to quantify it.
One thing I've noticed is that a TS with one ignition functioning will pull just fine up to about 3500 to 4000 rpm, then start to fall off. It'll run up to 6000 no problem in the lower gears, is just feels a bit dead. I assume this is because the flame front has time to get across the combustion chamber at low rpm when it starts from a single, off-center spark plug to produce a pressure max somewhere near the optimum engine rotation angle. But, as the rpms increase, and there is less time available, max pressure in the cylinder comes too late to be optimum. Firing both plugs at the same time means the pressure pulse is more abrupt and, if timed properly, results in a higher pressure max at the optimum crank rotation to produce more power. But I'm a chemist not an engineer so I'm guessing.
At the end of the day, FI systems can provide more, and nicer, performance than carbs. There are different things to trouble shoot with FI when problems arrise and they take a bit of time to get used to. If you are starting a TS conversion from scratch and the application is mostly street driving, I'd say go Motronic. The basic bugs are all worked out and it'll cost a whole lot less than "aftermarket" FI. If you've completed a carb/DCOE TS "street" conversion, enjoy it. Just don't expec to blowoff the guys with Motronic FI, but don't expect to be left in the dust either. I think the carb setup results in a car that drives and looks more like a classic Alfa. That's important to some people and I respect it. However, if you have carbs, you should plan on visiting the gas station a bit more often than your Motronic powered friends. So far, I'm getting about 4 mpg better mileage with the Motronic TS than any of my other "street" Alfas.
__________________
Bruce Colby
Competition Director, AROSC
'65 Sprint GT (TS race)
'69 1750 GTV (TS street)
'71 Jr. Z (special occasions)
'89 E30 (the dark side)
----------------------------
'69 1750 Spider (sold )
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10-15-2004, 10:18 AM
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Location: SF Gay Area
Posts: 1,722
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Bruce,
Sounds like your street TS has about 120 wheel bhp now?  , The butt dyno isn't too sensitive, I doubt you can feel an increase of 5-6 wheel bhp. So if you can feel something, the increase must be around 10 wheel bhp or more. 120 wbhp is about 145 flywheel bhp (taking a 17% drivetrain less) which is inline with what others have seen on stock 75 TS.
For those who want mild performance, I think the stock TS, a Squadra Tuning chip, and headers are plenty for 150-160 flywheel bhp performance.
You get power and fuel economy. And the TS still sounds like a classic twincam.
Last edited by 75evo; 10-15-2004 at 10:21 AM.
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10-15-2004, 11:0 | |
